DE2205596A1 - Device for determining a physical parameter, in particular moisture testing device for grains - Google Patents

Description

Device for determining a physical parameter, in particular Moisture tester for grains The invention relates to a device for determination a physical parameter, which has an electrical quantity in a given, in particular is linked in a variable manner, in particular a moisture tester, preferably for grains.

In general, the present invention is concerned with electrical Circuits for measuring the frequency of an input signal, specifically in the strict sense mit.frequency indicating circuits which contain devices to establish the relationship between the frequency of the input signal and the output signal of the circuit change in order to compensate for known physical phenomena and in particular with moisture testers for grains, which provide a digital display and Have facilities to measure the physical properties of the grains to be tested, the temperature of the particular sample being tested and the changes in circuit parameters of the tester to automatically compensate itself, Although the invention below in the context of a grain moisture tester is understood it will be apparent to those skilled in the art that they have a much broader scope owns.

Moisture testing devices have long been known. They mostly contain a cell consisting of two spaced electrodes between which thus a measured amount of based on their moisture content testing grains can be introduced. With the known moisture testing devices electrical circuits are provided that allow the difference between the electrical To determine the capacity of the cell between its full and empty state.

This difference in capacitance is of course an indication of the dielectric constant of the grains introduced into the cell, which in a simple way with the moisture content the grains to be tested can be linked.

Many moisture testing devices have been proposed in the past been. Most of them used some type of impedance device, which either changed manually or automatically. In your In general, the known moisture testing devices contain conventional devices for comparing the capacities of the cell and the variable impedance devices and means for adjusting the variable impedance to a predetermined one Relationship between these capacities is obtained, being the size of the required The setting shows the cell capacity and thus the dielectric constant of the Grains and thus their moisture content. The.

Conversion of the determined capacity values into the value for the moisture content was often done with the help of some kind of graphical representation. However, since the relationship between dielectric constant and moisture content Different for different varieties of grains had to be tested for each one Rornart can use its own scale. Since this relationship is also related to the Temperature of the grains changes, the measurement result usually had to be in Be corrected with regard to the respective temperature. In this context Reference should be made to U.S. Patents 3,051,894 which discloses an impedance display device as well as an earlier registration of the applicant (file number:.

Ser.No. 33 326), which also has an impedance measuring circuit and was filed in the United States on April 30, 1970. Furthermore, the Reference may be made to U.S. Patent 3,231,814 which discloses an apparatus for measuring and recording of capacitance properties describes at which the physical properties of the element with variable impedance depending on the one to be examined Grain variety can be changed by hand so that the moisture content is different Types of grains can be read from the same scale.

The present invention was based on this prior art now the task underlying a moisture tester to propose which works automatically and which a direct digital display of the moisture content supplies.

Furthermore, the device should be able to easily measure various Grain types be switchable; it should temperature changes of the grain sample automatically compensate; and it should automatically make changes in its own operating parameters can compensate for how they are due to aging or as a result of temperature changes may occur. After all, the new test device should also be easy to operate be able to deliver reliable and very accurate results over a long period of time and in be able to take the measurements quickly.

This task is performed by a device of the type described above solved, which is characterized according to the invention in that devices for generating first electrical SiQ signals of predetermined length are provided that Control means are provided for electrically controlling the length of the first signals are that devices for generating a second electrical signal with a frequency proportional to the electrical variable are provided and that display devices are provided indicating the number of oscillations of the second signal during the duration show the duration of a first signal.

According to the invention, there are circuits for measuring the frequency a input signal is provided, in particular circuits that have an electrical Provide an output signal that is linked to the frequency of the input signal, and means are provided to assess the relationship between the input signal and to change the output signal, in particular devices for a moisture testing device, which are the physical properties of the type of grain to be tested, the temperature the sample of grain to be tested and changes in the parameters of the electrical components automatically compensate for the test circuit.

It is an advantage of the present invention that it is an improved Frequency measurement circuit suggests.

It is another advantage of the present invention that it is a Frequency measuring circuit suggests in which the relationship between de.m output signal and the frequency of the input signal according to a variety of predetermined properties can be conveniently changed. Furthermore, it is an advantage of the present invention that it proposes a moisture tester which is easy to determine the moisture content of a wide variety of materials can be adjusted.

It is also an advantage of the present invention that it is a moisture tester suggests which automatically takes into account the temperature of the material to be tested or compensated.

It is also to be regarded as an advantage of the present invention that she suggests a humidity tester, which is based on the temperature of the test Material and which delays the delivery of an advertisement until the temperature of a temperature-sensitive element the temperature of the element to be tested Materials achieved.

It is also an advantage of the present invention that it is a moisture tester suggests which contains an automatic balancing circuit with the help of which Changes in the circuit parameters of the test device are compensated for.

Another advantage of the present invention is to be seen in that she suggests moisture tester with which the frequency of an oscillator can be determined which contains a capacity that is at least partially dependent on the test material is influenced, the tester having a digital display supplies.

Finally, it is an advantage of the present invention that it proposes a moisture tester, which stands out for its simplicity and reliability its operation, the accuracy of the results and the simplicity and economic efficiency of its structure and construction.

Further advantages and details of the invention are provided below explained in more detail with reference to a drawing and / or are the subject of the protection claims. The drawings show: FIG. 1 a perspective illustration of a moisture testing device according to the present invention, FIG. 2 shows a partial section through the moisture testing device according to Fig.l, Fig. 3 is a block diagram of part of the electrical circuit of the Moisture testing device according to Fig. 1, Fig. 4 (a) to Fig. 4 (e) diagrams for explanation the relationship between moisture and capacity in an inventive Moisture testing device for different types of grains, Fig. 5 is a schematic Representation of the electrical circuit of the moisture tester according to Fig. 1, Figures 6, 7 and 8 are schematic representations of further circuit parts for the moisture tester according to Fig. 1, Figures 9 and 10 are a block diagram and a schematic, respectively Representation of a circuit for temperature correction and temperature difference delay for a moisture testing device according to Fig.l.

Description of a Preferred Example In the following The present invention is intended to be described in the context of a moisture tester for grains or the like. can be described which provides a digital display. It However, it is understood by those skilled in the art that the basic idea of the present invention can find a much broader application and not to what is specifically considered here Embodiment is limited.

First, the overall structure and the mode of operation of the based moisture tester 10 disclosed in the accompanying drawings will. The moisture tester 10 has a number of on its front Buttons 12. One of these buttons is the main switch that controls the power supply for the tester can be switched on and the other buttons are used depending on The circuits of the testing device differ from the type of grains to be examined to select when depressed.

A funnel 14 protrudes partially and partially into the testing device over its top and serves to hold the grain sample to be examined. As can be seen from FIG. 2, the funnel is via a set of parallel rods 18 and springs 20 connected to a bracket 16, which in turn is fixed to the housing of the test device is connected, such Suspension on two opposite sides of the funnel is provided. The poles 18 are pivotable both with respect to the funnel 14 and with respect to the holder 16 and springs 20 are arranged to pull up the funnel. Of the The funnel and the spring system are pretensioned and there are stops provided that limiting the upward and downward movement of the hopper Wenn when a given weight of material is in the hopper, it vibrates this between the upper and lower stops and provides a positive indication the right weight. The funnel has flaps 22, which on his Underside are rotatably attached and opened by actuating a button 24 and can be closed, which are mechanically connected to them and at the Is attached to the top of the tester. A similar hopper and weighing system is in its details in an earlier registration of the applicant (file number: . . . . . Ser.No. 43 770), filed in the United States on June 5, 1970 became.

In the PrS device and below the funnel 14 is a granule cell 24 arranged. This cell 24 comprises a hollow, cylindrical, metallic outer Electrode 26, which is shown in section in FIG. 2, as well as a cylindrical, coaxial therewith metallic inner electrode 28 which has a conical cover at its upper end 30 owns. The cone shape of the lid 30 ensures that the grain samples that are released from the funnel 14, relatively uniformly in the annular Space between electrodes 26 and 28 can be distributed. The distance between the In addition, electrodes are made of insulating material by a construction (not shown) maintained. At the lower end of the cell 24, two drop flaps 32 can be pivoted arranged, which are preferably under a spring tension and which are in closed State the bottom of the Cell form, as shown schematically in Fig.2 is indicated in solid lines. The drop flaps can be opened mechanically with a button 34 at the top of the tester must be connected in such a way that when pressed down the button open, as shown in Fig. 2 in dash-dotted lines, the grains in the cell 24 in a drawer 39 in the lower part of the testing device be distributed. The drawer 39 can be removed after completion of the test and the tested grains can then be poured out.

The test device 10 also has a digital display unit 36, the on the front surface and the relative humidity of the tested material in Visually shows percentages. The test device can also be equipped with a digital printing unit be provided, a slot 38 being provided on the front of the test device is through which a card can be inserted into the printer, which then when the button 40 on the top of the tester is depressed, the same numbers are displayed prints on the map displayed by the digital display unit 36.

The test device according to Fig.l contains electrical circuits, -the now on the basis of the block diagram according to Figure 3, which contains the essential circuits, should be explained in more detail. The circuit, the block diagram of which is shown in Fig. 3, initially comprises an oscillator 50, its capacitive frequency-determining element is formed by the cell 24. The output of the oscillator 50 is via a gate switch 52 connected to a digital counter 54, which counts the number of oscillations of the Oscillator 50 via the gate circuit 52 supplied signal counts. The output signal of the counter, which can be carried over a number of lines, is the digital display unit (display) and the digital printing unit (Printer) supplied, both of which are indicated by block 56. A clock 58 provides at its output pulses of a predetermined but variable pulse frequency. The pulses of the clock are first of all a reset input of the digital counter 54 is supplied to an initial reference count in this when the pulse is switched on set, and second a control input of the gate circuit 52. The output signal of the oscillator 50 is thus sent to the counter 54 only for the duration of the pulses from the clock 58 is applied. When the duration of the clock pulses and the operating conditions of the oscillator 50 are known, the counting result displayed by the display unit 56 can used to determine the frequency of the oscillator, the capacity of the cell, the dielectric constant of the grains in the cell and to determine the moisture content of these grains.

Figs. 4 (a) to 4 (e) show the relationships between the percentages Moisture content and relative capacity for five varieties of grain, viz Corn, wheat, oats, soybeans and flaxseed, all at a constant temperature. The absolute value of the capacitance, recorded along the horizontal axis, will of course change with the actual dimensions of the cell used. In Figures 4 (a) through 4 (e) also show sets of five straight lines, and although one for each grain type, these lines going through the ends of the curves for the respective grain type are drawn through and as linear approximations of the assigned curves can be viewed. Each of the curves in Figs. 4 (a) through For the sake of simplicity, 4 (e) can be viewed as the sum of two functions, one of which is represented by the respective straight line while the other is equal to the difference between the actual curve and the straight line. With regard to the representations according to FIG. 4, the following appears useful record four observations: 1. For the recorded values the difference function is always positive, which indicates that the curves shown are all curved upwards.

2. For the types of grains examined, the have difference functions all of a similar shape, with a maximum value of about the same The relative capacity value is present, although the maximum values are strong differentiate.

3. The types of grains considered in Figures 4 (a) through 4 (e) can be divided into two groups, namely the cereal grains (maize, wheat and oats) and in the feed (soybeans and flaxseed). The slopes of the linear approximation functions for the grain types are roughly the same and the slopes of the approximate linear functions for the feed are also almost the same. For the types of grain, however, the result is a relatively larger one Slope than for the feed.

4. The maximum values of the difference functions for the feed are relatively larger than the maximum values of the difference functions for the grain types.

When evaluating the first three of the observations listed above one recognizes that if the shape of the difference function and the location of their As a maximum, each of the curves of Figures 4 (a) to 4 (e) is known by three parameters can be approximated well, namely by the intersection of the linear approximation function with the vertical axis, through the maximum value of the difference function and through the type of grain (type of grain or feed), this last parameter being one The measure for the slope of the linear approximation is. As explained in more detail below should be, do the described here Moisture tester according to the present invention use of precisely these parameters. The universal one The resonance curve is used as an approximation of the difference function.

It is well known that temperature changes lead to all types of spine a considerable vertical shift of the curves according to FIG. The relationship between this shift and the temperature is approximately linear and moreover the same for all types of grains commonly encountered. In the moisture tester according to the present invention are therefore devices for bringing about the vertical Displacement planned It is now intended to return to the discussion of FIG will. As stated above, if the duration of the pulses from the clock 58 is fixed, a simple relationship between the count obtained in the counter 54 is established at the end of each clock pulse and between the frequency of the oscillator 50, the Capacity of cell 24 and the moisture content of the grains in the cell. These Relationship is approximately linear because of the capacitance of the cells and the oscillator frequency as well as the moisture content of the grains and the dielectric constant approximate are parabolically linked. The change in the duration of the clock pulses changes this relationship. By properly setting the duration of the clock pulses, the relationship between the frequency of the oscillator 50 and the count obtained in the counter 54 can be set so that the relationship between the obtained counting result and the moisture content of the grains is the same regardless of the The nature of the grains examined and the temperature thereof. Furthermore, the display and the printer can be set to give a direct display of the moisture content deliver or print out the moisture content directly in Fig. 3 Four separate circuits are provided to adjust the length of the pulses at the output of the clock 58 are generated to change, namely a balance circuit 60 showing all deviations of the circuit parameters from their desired Compensated for values, a temperature circuit 62, an intersection circuit 64 and a curvature circuit 66. Although this is not shown in Figure 3 for the sake of simplicity a circuit can also be provided which effects those changes those corresponding to the observed differences between cereals and feed required are.

The balance circuit 60 is used to establish a fixed initial condition set for the test circuit. It is coupled to the output of the counter 54 and its operation is controlled by the output of the clock 58. The balance circuit generates a signal at its output which indicates whether the counter 54 on End of each clock pulse reached a count above or below a certain predetermined fixed number. If this output signal appropriately corresponds to the Clock 58 is fed, as shown in Figure 3, results in a feedback loop, via which the clock generator 58 is regulated in such a way that the counter 54 receives the fixed counting result reached, which is set in the balance circuit. The balance circuit works only when there are no grains in cell 24.

The temperature circuit 62 changes the clock frequency of the clock generator 58 in accordance with the temperature of the grains to be examined. It contains a thermistor 68 located in cell 24 and with those to be tested Grains is in contact. The change in resistance of the thermistor is evaluated, to generate an output indicative of the temperature of the grains and the clock 58 is supplied.

As will be explained below, the temperature switch be stopped when the Ealance circuit 60 is working, so that it meets the initial conditions The intersection circuit 64 supplies a Output signal which the clock frequency of the clock 58 in accordance with the position of the intersection of the moisture curve of the grains to be tested with the vertical axis changes. This change is made by choosing a suitable resistor for an element in the intersection circuit 64, which is shown schematically in FIG is indicated as a variable resistor 70.

As with the temperature circuit 62, the intersection circuit must also 64 must be switched off when the balance circuit is working.

The curvature circuit 66 finally changes the clock frequency of the Clock 58 in accordance with the relative capacity of cell 24. An output of the oscillator 50 is connected to the curvature circuit 66, which as an output signal provides an alternating current signal of constant amplitude, regardless of the Frequency of the oscillator 50. The alternating current signal of constant amplitude is one Parallel resonance circuit 74 supplied, which is tuned to the frequency with which the oscillator 50 operates when the capacity of the cell 24 is equal to that at which the actual moisture content of the grains has the greatest deviation possesses the rectilinear approximation function. Above the resonance circuit is thus an alternating voltage is generated which ynit the alternating current via the universal resonance curve linked by the circle. The alternating voltage is rectified by a diode 76 and then filtered so that a direct current signal is obtained, which is analog for the deviation of the straight-line approximation function of that actually is the curve applicable to this type of grain. The Ywumung circuit 66 has a variable resistor 72, which is indicated schematically and is used for 1 the magnitude of the alternating current signal with the constant current in accordance with the maximum deviation of the grains to be tested. It didn't proved necessary to use the curvature circuit while working the balance circuit 60 switch off. The curvature circuit generates due to the frequency of the oscillator 50 and the resonance frequency of the resonant circuit 74 only an output signal with one very low level when the tester is operating under the initial conditions.

From the above explanation it is clear that the intersection point and temperature corrections by changing the clock frequency of the clock a fixed clock frequency can be brought about. So now such a change has a known, fixed influence on the output signal of the test device assume that the oscillator 50 operates at a constant frequency. This assumption is of course flawed as it is the basic working principle of the Tester is to measure a change in the frequency of the oscillator. The relative The ending% of the oscillator frequency can, however, be compared to the actual frequency can be kept quite small. Under these conditions the above is then Assumption approximately correct.

The block diagram according to Figure 3 also includes control circuits for Control of the operation of the test equipment There is a flip-flop 80 for filling and emptying provided, which is a common flip-flop mi + a set and a Reset input is operated by switches that are mechanically connected to the Buttons 24 and 34 are coupled on the top of the tester. When the button 24 is depressed to allow the grains to enter the cell, alternates the flip-flop 80 to a first state and changes accordingly an output 82 of the flip-flop shows its state. This signal change is spread over a delay circuit 84 to the clock 58 and causes it to one To send out a clock pulse and to put the test device into operation.

After the test has been completed and the reading taken, the button 34 is depressed and the grains are poured out of the cell. At the same time, the flip-flop 80 goes into its second state and a signal at the second output 86 of this flip-flop changes and activates a feedback gate circuit (Feedback) 88. Activation of the feedback gate circuit 88 has two effects. Firstly, it has the consequence that the clock 58 from a feedback clock (R, clock) 90 a pulse is supplied, so that this is a further pulse predetermined Length and, secondly, it causes the return gate circuit to remain open until the flip-flop 80 changes state again. The output of the clock 58 is applied to one input of the feedback gate circuit 88. When the return gate circuit 88 is open, it consequently receives the output pulses of the clock generator 58 and reactivates this after a predetermined delay caused by the feedback clock will. Thus, the tester is the flip-flop 80 in its second state as long remains, continuously activated and can be the predetermined by the balance circuit Achieve condition. Tilting the flip-flop 80 to its second state switches the temperature circuit 62 and the intersection circuit 64 from simultaneously. Located if the flip-flop 80 is in the first state, then of course the balance circuit is switched off. The delay circuit allows the thermistor a sufficiently long time to get the temperature of the grains to be tested before taking a measurement will. So when button 24 is pressed, becomes the flip-flop 80 is tilted into its first state and the test device is switched to the "Display" mode switched. On the other hand, when the button 34 is operated, the flip-flop 80 is in flipped its second state and the tester works in the operating state "Balance". A schematic circuit diagram of a circuit according to a first embodiment the present invention is shown in Fig.5. The oscillator 50 is here essentially a Hartley oscillator that uses cell 24 as a capacitive element contains in its resonance circuit. The cell is actually connected in series 24 and a capacitor 100 parallel to one tunable by means of a coil core Inductance 102 and to a trimming capacitor 104, namely between a circuit point 106 and earth. The circuit point 106 is via a coupling capacitor 108 with the Gate electrode of a field effect transistor 110 of the p-type connected, which: in turn is connected to ground via a bias resistor 112. The source of the transistor 110 is connected to a tap of the inductor 102 and the drain electrode is connected to a first positive voltage source V1 via a load resistor 114 connected as well as a filter capacitor 116 to earth and also to the Transistor 118. The emitter of transistor 118 is connected to ground via diode 120 connected, with the cathode connection of the diode connected to ground, the base of the transistor 118 is connected to the source of transistor 110, transistor 118 is connected in parallel to transistor 110 as a shunt regulator and is used to to keep the amplitude of the output signal of the oscillator constant, independently changes in cell impedance and changes in circuit parameters of the Oscillator, as they can occur, for example, as a result of aging and regardless of changes in the voltage of the savings source V1. With one device According to the present invention, the circuit constant has proven to be favorable of To choose the oscillator 50 so that when the cell 24 is not filled with a frequency worked by 2 Niiz.

The output of the oscillator 50 is at the tap of the inductor 102 tapped and via the series connection of a resistor 122 and a capacitor 124 is applied to a node 126, which in turn has a resistor 130 is connected to a node 128. A conventional OR gate 132 with two inputs is connected to both inputs at node 126 while being Output is connected to node 128. The description of the OR gate 132 and all other elements, which are described below in their logical functions should be made according to the assumption that a positive voltage level represents a logic "one" while the ground potential represents a logic "zero". The OR circuit 132 is used to amplify the output signal of the oscillator 50 and converts its sinusoidal output signal into a pulse-shaped output signal which is fed to the counter 54. The pulse-shaped signal is generated by the Circuit point 128 via a resistor 134 to a first input of another conventional NOR catters with two inputs, which the gate circuit 52 in Fig.3 forms.

The clock generator 58 is basically a monostable multivibrator with facilities for changing its period.

The trigger input of the clock is at a circuit function 140, which is connected to the anode of a diode 142, its cathode-side connection is connected to the base of an npn transistor 144. Node 140 is furthermore connected to the circuit point 128 via a capacitor 145. Of the The emitter of the transistor 144 is on the one hand via a resistor 146 to ground and on the other hand, connected directly to the emitter of a further npn transistor 148. The collector of the transistor 144 is on the one hand via a resistor 150 with a first positive voltage source V1 connected and on the other hand to the base of a pnp transistor 152, while the collector of transistor 148 connects directly to the first positive voltage source V1 is connected. The base of transistor 148 is with connected to the circuit point 153, which in turn via a capacitor 154 is on earth. The collector of transistor 152 is connected to a node 155 and its emitter is connected to the first positive voltage source V1. Node 155 is both through resistor 156 to ground and across a resistor 158 connected to the base of a pnp transistor 160, the collector of which with a node 153 and its emitter via a resistor 162 with the Base of transistor 144 is connected and through a resistor 164 with the first positive voltage source V1 and also through a resistor 166 to ground. The output signal of the multivibrator 58 is picked up at the node 155. This circuit point is via the parallel connection of a resistor 168 and a capacitor 170 is connected to the base of transistor 144.

The capacitor 154 serves as the element determining the period of clock 58. The emitter of transistor 160 is normally with the help of a voltage divider of resistors 164 and 166 at a fixed positive voltage held. The output signal of the clock at node 157 is at the Embodiment described here normally to reference potential, and it positive pulses are sent out when the clock is energized. In this way the transistor 160 is normally conductive1 and the node 153 is normally held at the bias voltage for the emitter of transistor 160. Resistors 162 and 168 serve as a further voltage divider between the potentials at the EYnitter of transistor 160 and at node 155 so that the base of the Transistor 144 is normally biased low. The positive Potential at node 153 tends to make transistor 148 fully conductive to make, so that a positive signal appears at the emitter of transistor 144, which tends to turn this transistor off. When the transistor 144 is normal, its collector is also at a high positive Potential and the transistor 152 is switched off.

If a positive triager pulse of sufficient amplitude is sent to the one Node 140 representing the input becomes the base of the transistor 144 positive enough to control this transistor fully conductive, whereby the Voltage at the collector of this transistor drops and so does transistor 152 becomes fully conductive, which in turn increases the potential at the circuit point serving as the output 155 increased approximately to the voltage of the first positive voltage source V1 will. This voltage rise is caused by the voltage divider from the resistors 162 and 168 that the base of transistor 144 remains positive enough that this transistor is kept in the fully conductive state. The conductive state of transistor 144 also raises the voltage across resistor 146 so that the Transistor 148 becomes relatively non-conductive.

However, the voltage rise at node 155 is also sufficient, to drive transistor 160 to a relatively non-conductive state. In order to however, the capacitor 154 may charge at a rate that depends on the Size depends on the direct currents supplied to it. When the charge of the capacitor 154 reaches a sufficiently high level, the base of the Transistor 148 is again forward biased, so this transistor becomes fully conductive. In this way, one arrives at the emitter of transistor 144 positive voltage, which is almost equal to the voltage from voltage source V1, so that it becomes relatively less conductive, as a result of which transistor 152 is also less becomes conductive and as a result of which the potential at circuit point 155 is approximately up again Reference potential is fed back.

It is thus evident that by changing the loading speed of capacitor 154 the duration of the positive pulse at the output serving Circuit point 155 can be changed. In the circuit described, the Capacitor 154 is charged by signal currents given to it by the balance circuit 60, temperature circuit 62, intersection circuit 64, and curvature circuit 66 are fed. In a device according to the present invention with a Oscillator 50, which normally operates at a frequency of 2 MHz, proved it is favorable to choose the switching constants of the clock 58 so that its Output pulses were about 1 millisecond long when from the circuits 60, 62, 64 and 66 no signals were applied. The circuit parameters of the clock generator can are preferably selected so that an output pulse of the Oscillator 50 must be present to trigger the clock.

The clock generator can be synchronized with the oscillator in this way will.

Node 155 forming the output of the clock is across a resistor 180 to the two inputs of one usual NOR gate 182 connected, which in the present circuit as an inverting signal amplifier serves and its output via a resistor 184 to a second input of the Gate circuit 52 is connected. The positive pulses at node 155 will be thus converted into negative pulses and used to control the gate circuit 52. The gate circuit 52 designed as a NOR gate is inverted by the Output pulses of the clock and open and during the duration of these pulses serves to allow only those pulses from the oscillator 50 to pass to the counter 56, the pulses of the clock 58 occur during the duration of the output.

The flip-flop 80 for filling and emptying is normally used by one open filling switch 190 actuated, the mechanically with the button 24 on the top of the test device is connected, as well as through a normally open drain switch 192, which is mechanically connected to the button 34 on the top of the test device is. The switch 190 connects a second positive voltage source V2, the one supplies lower voltage than the first voltage source V1, with a first input a conventional, two-input NOR gate 194 in flip-flop 80, this input is at the same time connected to earth via a resistor 196. The desk 192 connects the second positive voltage source V2 to a first input of a another conventional two-input NOR gate 198, this input is also connected to earth via a resistor 200. The output of the NOR gate 194 is connected to the flip-flop output 86 and the second input of the NOR gate 198 connected, while the output of the NOR gate 198 to the flip-flop output 82 and to the second input of the NOR gate 194 is connected. If the switch 190 is actuated briefly, a appears at the output 82 positive voltage and earth potential at output 86. If, on the other hand, the switch 192 is operated briefly, a positive potential appears at output 86 and at Output 82 earth potential.

A conventional digital counter 202 which, as output signals, has both provides a binary encrypted decimal signal as well as a decimal signal with its signal input at the output of the NOR gate 52. When the oscillator 50 with a frequency of approximately 2 MHz and if the clock 58 pulses with a duration of approximately 1 millisecond are generated during the counter 202 a clock pulse supplied approximately 2000 pulses. In addition, this increases Filling grains into the cell 24 their capacity, thereby increasing the frequency of the Oscillator 50 drops and thus also that of him during a single gate pulse number of pulses delivered to clock 58. The highest count, whichever the counter 202 must be able to store, is thus around 2000. However, it has found that when operating a circuit with the above-mentioned time parameters the maximum frequency change of the oscillator is only about 10%.

The thousand digit of the counter result is therefore relatively insignificant, and therefore only the last three correct numbers are stored by the counter 202. A digital counter with a maximum count of 999 can be used.

The decimal outputs of counter 202 go in parallel with the digital Display unit 36 and the digital printing unit connected. As can be seen from Fig. 4, with an increase in the moisture content of each type of grain to be tested, the Capacity of cell 24 increases, thereby increasing the frequency of the oscillator 50 is lowered and whereby the reached during a single clock pulse Count of the counter 202 is decreased. thus the digital display unit 36 provides a direct indication of the moisture content of the grains, this must be indicated Counting result when the count reached by counter 202 decreases increase. The display unit 36 and the printer are therefore constructed so that they display the nine's complement of the count of the counter 202.

In fact, between the pulses of the clock, they show the last three important digits of the number 2000 minus the number of the oscillator pulse that were counted during the previous clock pulse.

The output 82 of the flip-flop 80 is connected via a capacitor 204 a first input of a conventional, two-input NOR gate 206 connected, this first input at the same time via a resistor 208 Earth lies. Further, the inverted output of the clock 58 from the second The input of the gate circuit 52 is tapped and via an inverting amplifier 210 is applied to a node 212.

This node is connected to the second via a capacitor 214 Input of the NOR gate 206 coupled, this second input via a resistor 216 is also connected to earth. An inverting amplifier 218 is with his The input is connected to the output of the NOR gate 206, while its output is connected to the reset inputs of the counter 202 is connected. These. Reset-input-set-at If there is a positive pulse, the count of the counter 202 is set to 999, so that the display unit 36 now shows zero.

It is obvious that the series connection of the NOR gate 206 and inverter 218 forms an OR gate. When the output of the clock 58 becomes positive and thus the Indicates the beginning of a cycle time this voltage change in the positive direction via the inverters 182 and 210 to the Circuit point 212 applied. A capacitor 214 and a resistor 216 differentiate the positive voltage rise and deliver a short positive pulse, the one corresponds to a logical "one" to the NOR gate 206, with the result that a positive pulse of corresponding duration is applied to the reset inputs of counter 202 is, causing the counter to receive the pulses from the oscillator 50 for the the following cycle time is being prepared. Similarly, the voltage change in the positive direction at the output 82 of the flip-flop 80, which when the Switch 190 enters, via a differentiating circuit from a capacitor 204 and a resistor 208 is applied to NOR gate 206, with the result that a short positive pulse is applied to the reset inputs of counter 202. These measures have the advantage that the digital display unit 36 during the delay introduced by the delay circuit 84 is displayed as zero will.

The output of clock 58 at node 155 is over a resistor 220 in the feedback gate circuit 88 of the base of an npn transistor 222 supplied. The collector of this transistor is through a resistor 224 m9 connected to the circuit point 140 of the clock generator 58, which serves as an input, and also via a resistor 226 to the first positive voltage source V1 as well as via a capacitor 228 which serves as a feedback timer 90 to ground. So as long as that the output signal of the clock generator 58 is positive, i.e. during the duration of a clock pulse, the transistor 222 is conductive and the capacitor 228 discharges through it. As soon the clock pulse ends, transistor 222 from clock 88 becomes a positive Signal is fed in and it becomes non-conductive. Of the capacitor 228 then charges through resistor 226 until the voltage across it reaches a level Reaches level high enough to trigger clock 58. The return gate circuit 88 and the feedback timer 90 thus trigger the timer 58 again at the end of a predetermined period that follows the end of a clock pulse, the length of this Period primarily depends on the relative values of resistor 226 and capacitor 228 depends.

To trigger the clock 58 when the cell 24 is filled with grains are, the output 82 of the flip-flop 80 is via the series connection of resistors 230 and 232 coupled to the base of transistor 222. However, it is a delay circuit 84 provided in order to delay the activation of the clock until the thermistor 68 has reached the temperature of the grains. The output 86 of the flip-flop 80 is connected to a resistor 234 in the delay circuit 84, which in turn is connected to the base of an npn transistor 238 via a capacitor 236. The emitter of transistor 238 is directly connected to the second positive voltage source V2 while the base and collector of transistor 238 are connected via resistors 240 and 242 are connected to the first positive voltage source V1. The collector of transistor 238 is also connected via the series connection of two capacitors 244 and 246 connected to a node 248 which is an output. This The circuit point can be connected to earth via a normally open switch 250 and also connected to the junction point of resistors 230 and 232 Da the voltage of the voltage source V2 is lower than that of the voltage source V1 is located. transistor 238 is normally conductive. If last for emptying the Cell the key 34 was pressed, delivers that Flip-flop 80 at its output 82 a signal of 0 volts.

If, however, the switch 190 is actuated via the key 24, appears a positive potential at the flip-flop output 82, which initially has the tendency keeping the base of transistor 222 at a positive voltage and thereby Feedback gate actions suppressed by not allowing capacitor 228 will recharge at the end of a clock pulse, further goes when pressed of the switch 190, the signal at the flip-flop output 86 to ground potential, whereby because of of capacitor 236 generates a negative pulse at the base of transistor 238 so that it becomes non-conductive. The values of capacitor 236 and des Resistor 240 are chosen so that the negative pulse drives transistor 238 for holds non-conductive for a relatively long time, for example for 10 seconds. the The voltage at the collector of this transistor rises approximately to the voltage of the Voltage source V1 appears at and at the circuit point 248 which forms the output a positive impulse. However, if the negative pulse at the base of the transistor 238 is sufficiently intercepted, this transistor becomes conductive again and the voltage at its collector drops from the voltage of the first positive voltage source V1 to that of the second positive voltage source V2, whereby at the circuit point 248 results in a negative pulse. This negative pulse becomes the base of the transistor 222 and lasts if the values for the resistor 242 and capacitors 244 and 246 long enough to allow capacitor 228 to pass to give to recharge, so that at node 140 a positive Voltage is created that is high enough to operate the clock 58. It should It should be noted that the actual connections to the flip-flop 80 of the Delay circuit 84, feedback gate circuit 88 and the feedback timer 90, as shown in Figure 5, slightly different from distinguish the connections shown in Fig.3. Otherwise the circuit leads however, according to FIG. 5, the same logical operations as those according to FIG. 3.

The temperature correction circuit 62 includes an npn transistor 260, its emitter with earth and its collector via the series connection of a Resistor 262 and a thermistor 68 connected to node 264 is. The node 264 is connected to the first positive voltage source V1 a resistor 266 and, through the series connection, a variable resistor 268 and a fixed resistor 270 with the collector of an npn transistor 272 tied together.

The emitter of transistor 272 is connected to ground while being Collector additionally via a resistor 274 to the base of transistor 260 connected is. The base of transistor 272 is connected to the first positive voltage source V1 connected via the series circuit of resistors 276 and 278, their connection point is connected to ground through a normally closed switch 280. Of the Output 86 of flip-flop 80 is through a resistor 282 to the base of the transistor 272 connected. The switching point 264 is connected to the switching point via a resistor 284 153 in the clock 58 connected.

When the transistor 272 by applying a positive voltage on its base, i.e. controlled by actuation of switch 192, becomes conductive transistor 260 is relatively non-conductive and the voltage at node 264 depends primarily on the voltage divider effect of resistors 266, 268 and 270 from. When the transistor 272 is made by applying ground potential to its base, for example by operating switch 190 made relatively non-conductive transistor X0 is opened and the voltage at node 264 is suspended then primarily from the voltage divider effect of resistors 262 and: 266 and the thermistor 68. The voltage at node 264 is then of the Temperature of the thermistor in the row depends. The variable resistance 268 is set so that the total resistance of resistors 268 and 270 at one any reference temperature, for example at 200 C essentially equal to that The total resistance of resistor 262 and thermistor 68 is. So if the Switch 190 is actuated, the voltage at node 264 changes in which it either becomes higher or lower, and a current flows through the resistor 284 through which the capacitor 154 in the clock 58 is either charged or discharged depending on the amount and sign of the temperature deviation the grain from the reference temperature.

The intersection correction circuit 64 includes a resistor 290, which is between the first positive voltage source V1 and a circuit point 292, which in turn is connected to a circuit point 296 via a resistor 294 connected is. Resistor 298 connects node 296 to the collector an npn transistor 300, the emitter of which is connected to ground. The node 296 is also coupled to the collector of an npn transistor 302 via a number of variable resistors, indicated collectively at 304 and which can be selectively switched on with the aid of switch 70. The switch 70 is one Schematic representation of part of the switches that can be operated with buttons 12- Front side of the test device are connected and with'den the desired circuit constants be selected for the type of grain to be tested. For any type of Grain becomes another Resistance selected, taking the simplicity sake only three resistors are shown in the drawing. The emitter of the transistor 302 is connected to earth. The base of transistor 300 is through a resistor 306 is connected to the output 86 of the flip-flop 80, while the base of the transistor 302 is connected to the flip-flop output 82 via a resistor 308. In the end is the circuit point 153 on the one hand via a resistor 309 to the circuit point 292 and on the other hand via the series connection of resistors 310 and 311 with the Collector of transistor 302 connected.

When the flip-flop 80 is in the "empty" state, will A positive voltage is applied to the base of the transistor 300, which this transistor controls conductive while applied to the base of the transistor 302 ground potential and keeps this transistor non-conductive. A voltage divider made up of resistors 290, 294 and 298 then creates a fixed voltage at node 292, the one Current through resistor 309 to node 153. If the flip-flop 80, however, is in the filling state, the transistor 300 becomes non-conductive and transistor 302 conductive. It then becomes a voltage divider made of resistors 290, 294 and a selected one of the resistors 304, the other fixed voltage generated at node 292, this voltage depending on which of the resistors 304 was selected and a current through the resistor 309, which charges or discharges capacitor 154, depending on how big the current is and which direction it has. The resistance of the series connection the resistors 310 and 311 is relatively large compared to the other resistors the intersection circuit, so this has little impact on operation to have.

The curvature correction circuit 66 is based on the output of the oscillator a5nge / steS St her via a resistor 320 at the base of an npn transistor 322 is fed. The base of this transistor is also through a bias resistor 324 is connected to the second voltage source V2, while the collector of the transistor 322 is connected directly to this voltage source. The emitter of the transistor 322 is on the one hand connected to earth via a resistor 326 and on the other hand to the base of an npn transistor 328. The emitter of transistor 328 is in turn connected to the Circuit point 330 connected via resistor 332 and via a bypass capacitor 334 with earth. The node 330 is connected to a voltage divider circuit, which includes a resistor 336 connected to the second voltage source V2 as well as one of a number of variable resistors identified by the reference number 338 are designated and which can be selected with the aid of a switch 72 which is marked with Earth is coupled. The switch 72 is a schematic representation of a portion those buttons 12 on the front of the tester with which the desired Circuit constants selected for the particular grain type to be tested will. A different resistor 338 is selected for each type of grain, where only three resistors 338 are shown in the drawing for the sake of simplicity.

The collector of transistor 328 is connected via resonant circuit 74 connected to the positive voltage source V2. The resonant circuit 74 consists of the Parallel connection of a capacitor 342 and an inductor 340, which by means of of a voting core is tuned. The collector of transistor 328 is also connected to the anode of a diode 76, the cathode of which is connected to a circuit point 344 lies, which on the one hand via the parallel connection of a resistor 346 and a filter capacitor 348 lies on earth and on the other hand over a resistor 350 in clock generator 58 is connected to node 153. Transistors 322 and 328 and their associated components amplify the output signal of the oscillator 50 and drive the resonant circuit 74. The amplitude of the resonant circuit The driving signal can be changed by selecting a suitable one of the resistors 338 will. In one embodiment of this invention in which the oscillator 50 had a nominal operating frequency of 2 MHz, resonant circuit 74 was for one Resonance frequency of 1.9 MHz designed.

The balance circuit 60 includes a conventional two-input circuit NOR gate 360, the first input of which is via the parallel connection of a resistor 362 and a capacitor 364 to ground, the inverted output of the Clock 58 is tapped from the second input of gate 52 and this first input of the NOR gate 360 supplied via a diode 366, the anode of which with is connected to the first input of NOR gate 360. The balance circuit includes also another conventional, two-input NOR gate 368, whose first input connected to node 212 in counter 54. A number of outputs of counter 202 is connected to inputs of a conventional AND circuit 370 connected to several entrances. The counter outputs are the ones that are approximate represent half the number of pulses generated during a single clock pulse of the clock 58 are generated by the oscillator 50. The nominal clock pulse duration is chosen to correspond to approximately 2000 pulses from oscillator 50. the Pinary outputs of counter 202 which, if correctly energized at the same time, a counter reading of 999 are connected to the inputs of the AND circuit 370 connected. The AND circuit 370 thus sends one corresponding to the logical "one" pulse off when the count of counter 202 passes t7ert 999. The outcome of the AND circuit 370 is via an inverter 372 with the complementary input of a conventional flip-flops 374 connected for setting and resetting. The Q output of the Flip-flops 374 connects to the complementary input of another conventional flip-flop 376 connected for setting and resetting. The flip-flops 374 and 376 are constructed so that the Q outputs deliver the logical zero in the set state, while the I outputs deliver the logical "one".

In the reset state, on the other hand, the C 'outputs are on the logical one "Eins" and the I-exits on the logical t'Sull ".

The flip-flops are triggered by a negative pulse applied to their complementary input is applied, while a negative pulse is applied to the reset input is applied, it causes it to adopt the deferred state. The I- and Q outputs of flip-flop 376 are connected to the respective second inputs of the gates 360 or 368 connected. The reset inputs of the flip-flops 374 to 376 are with connected to the output of gate 206 in counter 54.

The output of gate 360 is via an inverting Amplifier 378 and a resistor 379 fed to the base of a pnp transistor 380, the emitter of which is connected to the second voltage source 2. The outcome of the Gate 368 is made up of a resistor 381 and a capacitor 382 connected, the other end of which on the one hand directly to the base of an npn transistor 384 and on the other hand via a resistor 386 to earth. The emitter of the transistor 384 is connected to the output 82 of the flip-flop 80. The collectors of the transistors 380 and 384 are connected to one another via the series connection of two resistors 387 and 388 connected, the connection point of these two resistors via the series circuit one resistor 389 and one normally closed switch 390 is connected to the gate electrode of a field effect transistor 392. That The gate element of the field effect transistor is also provided via a capacitor 394 Connected to ground, while the source element is connected to the first via a resistor 396 positive voltage source V1 and connected to ground via a resistor 398. The drain of transistor 392 is connected to the first through a resistor positive voltage source V1 connected and also to the base of an npn transistor 402 in the clock 58 through a resistor 404. The base of the transistor 402 is also connected to ground via a resistor 405 and also to the emitter of the same transistor, via the series connection of a diode 406, which has its cathode at the base, with a resistor 408, a variable one Resistor 410 and a resistor 412. The connection point between the variable Resistor 410 and resistor 412 is connected to the output of the clock generator Circuit point 155 connected. The collector of transistor 402 is with the node 153 connected.

When the circuit 60 is working and the tester is in a balanced State is, the clock pulses at the output of the clock 58 have such a Duration that they include 2000 pulses of the oscillator 50. The count of the counter 202 thus goes through the value 999 three times during each clock pulse, namely that first Ft1 when the counter is activated by applying an appropriate signal from the output of the Gate 206 is set to this value at the beginning of the clock pulse, the second Times when the thousandth pulse arrives from the oscillator 50 via the gate circuit 52 and the third time when the two thousandth pulse from the oscillator arrives 50 via the gate circuit 52. When the counter passes the value 999, appears positive pulse or a logical "one" on Output of the AND circuit 370 and arrives from there via the inverter 372 as a reference potential or as a logic zero to flip-flop 374.

At the beginning of each clock pulse, the flip-flops 374 and 376 reset by a pulse from gate 206.

The first pulse from AND circuit 370 thus sets the flip-flop 374, so that the signal level at its Q output depends on a positive voltage or a logical "one" changes to ground potential or a logical "zero". This signal change in turn sets the flip-flop 376, so that the Signal level at its output vop "zero" to "one" changes and at its Q output from "one" to "zero". The second pulse from circuit 370 sets the flip-flop 374 without any effect on the flip-flop 376. The third Pulse from circuit 370 resets flip-flop 374, causing the flip-flop 376 is reset, with the result that the output of the flip-flop 376 goes from "one" to "zero" while the Q output goes from "zero" to "one". So when the tester is balanced, the output of the flip-flop is 376 is normally at the logic level "zero", with the positive fmpulse when changing to level "one" coincide with the clock pulses, like this is shown at A in Fig.3. The signal at the output is in the NOR gate 360 with the inverted clock pulses combined, which are normally at the logic level "On" lie, with negative pulses at the logic level "zero", such as this is shown at B.

The output of the NOR gate 360 is thus constantly at the logical Are "zero" (occasionally positive pulses with the logic level "one" occur at the output of gate 360, which are based on differences in the propagation times between the different parts of the circuit.

The network of resistor 36St, capacitor 364 and the diode 366 leads here to a slight delay, which helps to generate such impulses suppress. The occasional impulses would, however, always be very strong short duration and have no influence on the functioning of the subsequent circuits.> When the tester is balanced, the Q output of flip-flop 376 is normally at the "one" level, with negative pulses at the "zero" level with the clock pulses coincide as shown at C. The Q output is with the clock pulses combined, which are normally at the logic "zero" level, with positive Pulses go to the logic level "one", as shown at E ", and although in the NOR gate 368. The output of the NOR gate 368 is also are constantly on "IQull".

(As with gate 360, logical "one" pulses may occasionally be present at the output occur, but this has no effect).

However, if the tester is not balanced, i.e. out of balance, another set of signals appears. If the clock pulse duration is too long or if seen differently -the frequency of the oscillator 50 is too low, exceeds the clock pulse duration is the time it takes for the counter 202 to pass two thousand Pulses are supplied. Thus, the "one" pulses are at the output of the flip-flop 376, which are applied to the second input of NOR gate 360, as in E is shown shorter than the inverted clock pulse, which is at the "zero" level and is fed to the first input of the gate. At the output of the NOR gate In 360 a positive "one" pulse appears, the duration of which is the same as that which is too long The length of the clock pulse is as shown at F. This impulse is from the Inverter 378 inverted and, as a negative pulse, the base of transistor 380 fed, as shown at G. lSnn the clock pulse duration is too short or if - different considered - the frequency of the oscillator 50 is too high - then the clock pulse duration too long to be able to feed two thousand pulses to the counter 2C2 before the gate circuit 52 is closed at the end of the clock pulse. The counter 202 will therefore become fewer than two thousand pulses are fed to the AND circuit 370 during a clock pulse only sends out two pulses, so that the flip-flop 376 does not go into the reset State returns. The zero at the output of the flip-flop 376r that at the second input of the NOR gate is applied, does not end with the end of the clock pulse, and it a "one" signal is applied to the first gate input as shown at H is. The output of the NOR gate 368 thus changes in the positive direction, "zero" to 'one', namely at the end of the clock pulse, as shown at I. This positive voltage jump is generated via the network from resistor 381, the capacitance 382 and resistor 386 as a positive pulse as shown at J, fed to the base of transistor 384.

In summary, it can be stated that if the clock pulse duration is too long A negative pulse is applied to the base of transistor 380 at the end of each clock pulse is, while if the clock pulse duration is too short, at the end of each clock pulse a positive pulse is applied to the base of transistor 384.

When the switch 190 is operated to fill, the emitter is turned on of transistor 384 a positive signal is applied, whereby the rest of the balance circuit is effectively blocked. However, if the switch 190 is operated to empty, the emitter is connected to earth potential and the balance circuit is activated. in the activated state have those applied to the bases of transistors 380 and 384 Impulses result in that their associated transistors fully conductive will. The conductive state of transistor 380 has the consequence that the capacitor 394 via the resistors 387 and 389 from the second positive voltage source V2 on while the conductive state of transistor 384 has the consequence that capacitor 394 discharges to ground through resistors 388 and 389.

The transistor 392 and its associated components serve as a voltage amplifier, which generates a voltage at the drain electrode that is inversely proportional to is the voltage across capacitor 394. The drain voltage is used in turn, to regulate the speed at which the current flows through the transistor 402 reaches the capacitor 154.

The clock pulses at node 155 serve as a bias for transistor 402. When node 155 is at zero volts, the transistor is 402 non-conductive; however, when node 155 is at a positive voltage is the emitter-base path of the transistor 402 through the resistors 408, 410 and 412 as well as by the voltage drop across diode 406 in the forward direction biased so that through the collector of this transistor a current flows to the capacitor 154 flows. The variable resistor 410 allows for proper adjustment the preload. However, from the drain electrode of transistor 392 is via the Resistor 404 is supplied with a current which tends to bias for reverse the emitter base path of transistor 402. The size of the transistor 402 of the current supplied to capacitor 154 is then inversely proportional to of the voltage at the drain electrode of transistor 342 and therefore directly to the Voltage across capacitor 394 linked.

So you can see that if the duration of the clock pulse is too long is, the transistor 380 is controlled to be conductive for a short time, on the one hand the voltage across the capacitor 394 is increased and on the other hand during the next following Clock pulse the current is increased via transistor 402 to capacitor 154, so that there is a tendency that the duration of this subsequent pulse decreases.

If the duration of the clock pulses is too short, the transistor conducts 380 for a short time and thus lowers the voltage across the capacitor 394 and the current to capacitor 354 via transistor 402 during the next one Clock pulse, so that there is a tendency that the duration of this next Impulse increased.

As mentioned above, in the moisture testing device according to the invention Circuits may be provided that allow the moisture content to both be monitored Easily measured in the same device for both grain and feed. In the embodiment according to FIG. 5, these circuits contain an npn transistor 420, the base of which is connected to the first positive voltage source V1 and also via a switch 124 with earth. The emitter of transistor 420 is connected directly to earth, while the collector on the one hand via a capacitor 426 with the ungrounded electrode of the cell 24 and, on the other hand, to the connection point of resistors 310 and 311 is connected. The switch 424 is mechanical with the Buttons 12 on the front of the tester are connected to the selection of the Serve grain genus so that it is closed when a button for grain is pressed while it is opened when a button for feed is operated.

When switch 424 is open, transistor 420 is conductive and capacitor 426 is connected in parallel with cell 24. Changes in relative Capacity of the cell have less of an effect on the frequency of the oscillator 50. Furthermore, the inclusion of capacitor 426 in the oscillator circuit lowers its working frequency and brings it closer to the resonance frequency of the oscillating circuit approach.

The effect of the curvature correction circuit 66 on the operation of the The test device is thus when the switch 424 is open when testing feed is relatively larger than when it is closed.

Opening the switch 424 also becomes the connection point of resistors 310 and 311 practically connected to earth, so that resistor 311, if the test device is working in the balance mode, it is bridged. The resistance 310, which has a considerably lower resistance than the resistor 311, thus becomes significant for the operation of the intersection circuit, where the overall effect is that for the capacitor 154 a discharge path is opposite Earth is created when the testing device operates in the "display" mode, so that the cycle duration is lengthened, resulting in the relatively flatter slope of the linear distribution functions for animal feed.

The normally open switch 250 and the normally closed switch Switches 280 and 390 are provided to facilitate calibration of the tester. These switches can preferably be connected to each other so that they can operate simultaneously can be operated. For the purpose of calibration, the test device is enabled first to come into a balanced state by turning the switch 192 for the emptying actuates and waits until the display unit 36 shows a constant zero supplies. The switch 390 is then opened, so that the Tension is maintained, which is necessary for equalization. Simultaneously the switch 250 is closed, whereby the return gate circuit 88 opens and switch 280 is opened, with transistor 272 forward is biased and the thermistor 68 is effectively removed from the temperature correction circuit turns off. Both the balance circuit 60 and the temperature correction circuit 62 are thus switched off and the clock generator 58 becomes continuous and cyclical connected. Of the variable resistors 304 and 338 assigned to ground then that of a certain grain area selected, pressed in one of the buttons 12 whose mode of operation is indicated symbolically in FIG. 5 by the switches 70 and 72 is.

While the tester is operating as a result of the switch 192 is still in a state for emptying, which is normally the Mode 'balance', the intersection switching is also effectively put out of operation because the transistor 302 is disconnected, and that of the Display unit delivered display is therefore independent of the setting of the selected of resistors 304. The selected one of resistors 338 is then set to a first predetermined display is supplied by the display unit 36. Afterward the switch 190 for filling is then depressed, thus for the tester an operating mode is set which would normally be the operating mode "Display", and the selected one of the resistors 304 is adjusted until a second predetermined one Ad is received.

This process is repeated for each of the selected pairs of resistors 304 and 338 repeats with the first and second predetermined displays for each Kind of grains are different.

The test device can then be put into operation in which the switches 250, 280 and 390 are switched back to their normal position.

In summary it can be stated that it is with the test device according to the present invention is possible, the various physical properties and temperatures of the grains to be tested into account by taking the length the clock pulses changed. The counting and display units are designed so that they provide a count or display that is inversely proportional to the number of generated in the oscillator 50 during a clock period of Impulses and is thus directly linked to the moisture content, the slope the linear approximation function for the humidity as a function of the relative Capacity of the cell is accounted for by having a nominal clock pulse duration adjusts. You can tell the differences by changing the nominal clock pulse duration take into account the slope of the approximation function for grain and for feed. In the case of the test device considered here, the change in the nominal clock pulse duration is achieved by effectively connecting resistor 130 in parallel with capacitor 154, in order to increase the clock pulse duration, which corresponds to a reduced increase. Of the different position of the intersection of the linear approximation function with the vertical axis, which is either a consequence of the different properties different types of grain or a consequence of the change in temperature of a particular one Type of grain, could ideally be achieved by adding or subtracting a fixed number to the Counter reading of the counter 202 or from the counter reading of the same or to the displayed one Value or the displayed value. In the inventive However, the circuit will change the location of the intersection by making small changes taken into account in the clock pulse duration, since the changes in the frequency of the Oscillator 50 are relatively small, so approximate the desired result is achieved. A shortening of the clock pulse duration corresponds to an increase the Location of the point of intersection, while a shortening of a lowering of the point of intersection is equivalent to. The upward curvature of the real curve for moisture above the relative capacity of the cell is finally taken into account in that depending on the relative capacity of the cell, there are slight changes in the Caused clock pulse duration. In particular, the clock pulse duration at the point shortened by the maximum duration where the difference between the actual curve and its linear approximation function is a maximum.

It is understood that the embodiment described above a test device according to the invention can be modified in various ways, Without leaving the inventive idea, some possible modifications are shown in Figs. 6, 7 and 8, in which a modified temperature correction circuit a modified balance circuit or a modified oscillator is shown are.

The temperature correction circuit according to Fig. 6 is used as a temperature sensor instead of a thermistor, a ribbon-like thermocouple 500. The thermocouple consists of two strips of approximately the same length made of different metals, preferably made of chromel and constantan, the ends of which are spot welded to one another connected so that they form a single long ribbon. The thermocouple is placed in the cell so that it is in contact with the grains to be tested. That Thermocouple can be twisted into a spiral and electrically insulating between two Brackets 502 may be attached which are attached to the inner electrode 28 of the cell are, as Fig.2 shows. The chromel side of the thermocouple is then connected to a first input of an operational amplifier 504 connected. The constantan side will on the one hand via a resistance 506 with a second positive Voltage source V2 connected and on the other hand via the series circuit of a resistor 508 and a variable resistor 510 to earth. A second entrance to the Operational amplifier 504 is connected in series with resistors 518 and 520 applied to the positive voltage source V2. Between the positive voltage source V2 and the connection point of the resistors 514 and 516 is a diode 522, the is polarized in such a way that there is a high positive conductivity towards this Connection point results. The operational amplifier is called a DC differential amplifier operated. Resistor 518 serves as a feedback element and its resistance value determines the gain in connection with the input resistance of the amplifier same. The network with resistors 514, 516 and 520 and with the diode 522 is used to bring about a DC shift at the amplifier output. The variable resistor 510 can be used to set up the temperature correction circuit to calibrate and to set the output of amplifier 504 to a predetermined value, when the thermocouple 500 is at a known temperature. The change in resistance the diode 522 with the temperature is used to compensate the voltages, due to the different metals at the connection points of the thermocouple 500 with the remaining part of the temperature correction circuit.

Switching means are also provided around the temperature correction circuit put out of operation if the test device is working in the nalance operating mode. A pnp transistor 530 has its emitter connected to the output of the amplifier 504 and its collector is connected to the second input of this amplifier. The base of the transistor 530 is connected to the output of the via a resistor 532 Amplifier 504 and above a resistor 534 to the collector an npn transistor 536 connected. The emitter of transistor 536 is to ground and its base is connected through a resistor 538 to a node 540 and via a resistor 542 to the output 86 of the flip-flop 80 for filling and emptying connected. The circuit point 540 is on the one hand via a normally closed switch 544 connected to ground and on the other hand via a resistor 546 with the first positive voltage source V1.

If the test device is operating in the "Display" state, the output is present 86 of the flip-flop 80 at a relatively low voltage so that the base of the Transistor 536 is kept at a low voltage and the transistor is relatively does not remain conductive. A small current flows through resistor 532, so that the base and emitter of transistor 530 are essentially on the same Tension. The collector-emitter resistance of transistor 530 is thus relatively large compared to resistor 518 and has only a relatively small influence onto the feedback path of operational amplifier 504. When the output 86 of the Flip-flops 80, however, is at a relatively high voltage, which indicates that the test device is working in the balance mode, then the base-emitter path is applied of transistor 536 has a strong positive bias that allows a large positive current flows through resistor 532 so that the emitter of the Transistor 530 becomes positive with respect to the base thereof.

The emitter-collector resistance of transistor 530 is thus high low and the feedback resistor 518 is practically shorted. The reinforcement of amplifier 504 is thereby reduced to a very low value and am No increment signal appears at the output of amplifier 504. The test device can thus come into a balanced state, with the temperature correction circuit is actually turned off.

The switch 544 is opened to calibrate the tester. If the Switch is open, a positive voltage is applied to the base of transistor 536, whereby the temperature correction circuit is switched off independently of the state of the flip-flop 80.

The temperature correction circuit according to Fig.6 has gene above that according to Figure 5 some significant advantages. The thermocouple 500 has essential larger dimensions than the thermistor 68. Thus, in the circuit according to FIG Fig. 6 also shows a larger amount of the grain to be tested in contact with the temperature-sensitive Element than in the circuit according to FIG. 5 and temperature differences in the sample tend to compensate for each other. In addition, changes in the Packing density of the individual grains in the area of the temperature-sensitive element less impact on the results obtained. Finally, it is the response time of a thermocouple is considerably shorter than that of a thermistor, so that the delay introduced by the delay circuit 84 can be reduced. In any particular application of the present invention, these advantages can of course be weighed against the additional costs of the operational amplifier, which is required because the thermocouple only has a relatively low voltage-temperature gradient owns.

7 shows a modified balance circuit 60 for use in a test device according to the invention. It is particularly suitable for use in such Circles thought out in which the operating conditions for the oscillator 50 and clock generator 58 are chosen so that 1000 oscillations of the Oscillator 50 occur. As FIG. 7 shows, the gate circuit 52 and the counter are 54 similar to those in Figure 2. In addition, corresponding parts are shown in FIG the same reference numerals and should not be discussed in more detail.

As in the embodiment according to FIG. 5, the capacitor 204, which is connected to the node 600 in the present example, with the Output 82 of flip-flop 80 connected.

Furthermore, the first input of the gate circuit 52, which is here with the Circuit point 602 is connected to the output of the oscillator 50 and the second input of the gate circuit 52 and the input of the inverter 210, which are connected to node 604 here are connected to the inverted output of the clock 58 connected. The counter 54 contains an additional coupling capacitor 606, which connects the output of NOR gate 206 to the input of the inverting amplifier 218 couples and a resistor 608 that connects the second input to the second positive Voltage source V2 couples.

The binary coded decimal signal outputs of the counter 202, the Representing the counter reading 999 are with the inputs of one having six inputs AND circuit 610 connected. The output of AND circuit 610 is through a resistor 612 connected to a first input of a NOR gate 614 having two inputs, this first input being connected to the anode of a diode 615, the cathode of which at the output of the NOR gate 206 and prevents the signal at the first input of NOR gate 614 goes positive when the output of NOR gate 206 is at a low voltage. The output of inverter 218 has a first input a two input NOR gate 616 connected. The output of the NOR gate 614 is connected to the second input NOR gate 616 and also to a first input of a NOR gate 620 having two inputs. that the NOR gate 614 and 616 interconnected to form a flip-flop are. The second input of the NOR gate 618 is connected to the circuit point 604 and the second input of NOR gate 620 is connected to node 212.

The output of the NOR gate 618 is one through the series connection Diode 622 and a resistor 624 connected to a node 626, wherein the anode of the diode is connected to the output of the NOR gate 618. The output of the NOR gate 620 is via the series connection of a resistor 628 and a capacitor 630 connected to the base of an npn transistor 632, the base also having a Resistance 634 is connected to earth.

The emitter of transistor 634 is directly connected to ground and the collector is coupled to node 626 via a resistor 634. The switching point 626 is connected to the source electrode of an n-channel MOS field effect transistor 636.

The gate electrode of this transistor is on the one hand with the output 82 of the flip-flop 80 connected via a resistor 638 and on the other hand via a normally open switch 640 to ground. The drain of the transistor is connected to the gate electrode of a junction field effect transistor via a resistor 642 644 connected to a p-junction and further through a capacitor 646 with Earth. The source of transistor 644 is connected to the junction of Resistors 648 and 650 connected which create a voltage divider between the first Form positive voltage source U1 and earth. The drain of this transistor is via a resistor 652 to the first positive voltage source V1 and via a resistor 656 connected to node 654. The output of the Balance circuit is tapped from node 654.

As in the exemplary embodiment according to FIG. 5, the counter is set to 999 set if there is a signal at the beginning of a clock pulse his Reset inputs is applied, which has the consequence that the output of the hold 610 goes to a relatively high voltage, namely to the logical nOne ". The output however, NOR gate 206 is low at the start of the clock pulse Voltage, namely on the logical "zero". The first input of the flip-flop 614 is thus held at the logic "zero" via diode 615. The reset pulse with the logic level "one" supplied by the inverter 218 then that the outputs of NOR gates 614 and 616 are set to logic "one" and the logical "zero" will go.

If the test device is in the adjusted state, delivers the oscillator gives a thousand pulses during each clock pulse.

As a result, the counter 202 returns to the count 999 and on At the end of each clock pulse, the logic “one” is output again at the end of each clock pulse. The output signal of the switchover 610 thus runs as it does under M in FIG is recorded. The output of the inverter 218, however, is as this is shown under N. The outputs of NOR gates 614 and 616, the applied to the partial first inputs of gates 618 and 620 are below 0 and P recorded. The inverted clock signal and the clock signal on the second inputs of NOR gates 618 and 620 are recorded as Q and R, respectively. The signals at the inputs of NOR gates 618 and 620 then become corresponding the gate function combined, so that the output signal of both gates is a constant low voltage, namely the logical "zero" is.

However, if the clock pulse duration is too long, the second has that The signal fed to the input of the NOR gate 618 has the curve shown under S. Furthermore, the count result in the counter 202 is over towards the end of the clock pulse the meter reading 999 run out. The logical "one" that goes with it is output by the AND circuit 610, has the consequence that the output of the gate 614 returns to the logical "zero", so that a signal profile results as it is plotted under O. The NOR gate 618 combines the below S and 0 signals shown to the signal shown under T, which is a contains positive pulse or a logical "one".

If the clock pulse is too short, it has the second input of the NOR gate 620 has the profile shown under U. Furthermore the counter 202 never reaches a count of 999, so that the output signal of the NOR gate 616 has the course shown under V. The NOR gate 620 combines the signals shown under U and V to a signal curve W, in which finds a positive voltage jump. This signal is transmitted through the differentiation network from capacitor 630 and resistor 634 converted to a positive pulse and supplied to the base of the transistor 632 as a signal Z. So if the clock pulse duration is too large, a positive pulse appears at the output of NOR gate 618 while if the clock pulse duration is too short, a positive pulse at the base of the transistor 632 appears.

These pulses are evaluated to determine the length of the clock pulse duration to change. When the flip-flop is in the "emptying" state, is its output 86 is at a relatively high voltage and transistor 636 is conductive. A positive pulse at the output of NOR gate 618 charges capacitor 646 during a positive pulse at the base of transistor 632 causes that capacitor to discharge across the transistor. The transistor 644 is used for scaling the voltage across capacitor 646 and, in addition, this capacitor from to isolate the following circuit. The output signal is from the node 654 is tapped and can be fed to the clock generator in a suitable manner. if the gate electrode of transistor 636 is at reference potential, either because the flip-flop 80 is in the "fill" state or because of it because the normally open switch 640 is closed for calibrating the tester is, transistor 636 becomes non-conductive and capacitor 646 then receives its Tension upright.

Fig. 8 shows a modified oscillator and control circuit like him can be used in a test device according to the invention. The circle contains a coil 700 which lies between two circuit points 700 and 704. The switching point On the one hand, 702 is connected to the first positive voltage source via a resistor 706 V1 and the other hand connected to ground through a capacitor 708, while the node 704 both via the series connection of a capacitor 710 with the cell 24 as is also connected to earth via a variable resistor 712 and also with the collector of an npn transistor 714. The base of the transistor 714 is with coupled to node 702 via a resistor 716 and also via the Series connection of a resistor 718 and a capacitor 720 with a tap of the coil 700. Furthermore, the base is made up of a resistor via a parallel circuit 722 and a capacitor 724 connected to ground. The collector of another npn transistor 726 of the circuit is connected to node 702, while the emitter this collector is connected to the emitter of transistor 714 and during the base with the junction of resistor 718 and capacitor 720 connected is. The components described so far form the basic elements of a relatively common LC oscillator in which the differential term is strong Ë from transistors 714 and 726 serves as an amplifier. The oscillator output signal is taken from the tap on the coil 700. The capacitor 708 holds the switching point r02 grounded in terms of alternating current, so that the coil 700 and the circuit consist of the Capacitors 710 and 712 and cell 24 are actually parallel to each other. In addition, switching devices can be provided in order to connect the capacitor 712 For testing feedstuffs, a capacitor 713 can be switched on, which is shown in FIG. 8 shown in dashed lines.

The circuit according to FIG. 8 also contains an additional component relative to the amplitude at the oscillator output in the event of changes in the impedance of the cell 24 keep constant. These switching means include an npn transistor 730, whose The base is connected to the tap of the coil 700 via a capacitor 732 and also via a resistor 734 to earth, the emitter of which is directly connected to earth and its collector via a resistor 736 to the first positive voltage source V1 via a capacitor 738 to earth and also directly to the base of the npn transistor 740 is connected.

The emitter of transistor 740 is connected to ground while its Collector connected to the emitters of transistors 714 and 720.

The transistor 730 generates a direct current signal at its collector, which is inversely proportional to the peak-to-peak value of the signal at the oscillator output where the AC component of the signal is derived from capacitor 738 will.

The signal is used to control the conductivity of the collector-emitter circuit of transistor 740 is used and thus the entire current flows through the output circuits of transistors 714 and 726-. Thus, if the oscillator output has the tendency Has, Increasing its size decreases the flow of current through transistors 714 and 726, which tends to decrease the oscillator output amplitude and vice versa.

As mentioned above, the grain moisture tester contains a delay circuit 84 for delaying the energization of the clock 58 by a fixed time in which there is a temperature-sensitive element - the thermistor 65 in the circuit according to FIG. 5 and the thermocouple 500 in the circuit according to FIG Fig. 6 - it is possible to assume the temperature of the horns to be tested. It has found that this fixed delay time has certain disadvantages. If namely the temperature difference between the grains and the temperature sensitive element is initially large, it can take a considerable amount of time for the temperature-sensitive element comes to the temperature of the grains. Typically these times are in the order of magnitude of 10 to 20 seconds and more. as An example of such a situation should be mentioned that the grains are in an open container at temperatures below 00 C while the test device is inside a relatively warm building. If on the other hand the temperature difference between the grains and the temperature sensitive element is only a few degrees from the start, only a very short time is required until the temperature-sensitive element has assumed the temperature of the grains. So that the tester is now accurate for a wide range of temperature differences Delivers results, the fixed delay time must be relatively long. this has As a result, the delay usually lasts longer when using the test device than would be required to adjust the temperature sensitive element to the temperature of the grains, making the time for obtaining the measurement results unnecessary is extended. It also gives itself that in the case of extreme Temperature differences the delay time is not long enough to make the inaccurate Measurement results are obtained.

It has therefore proven advantageous to use the temperature circuit 62 and the delay circuit 84 in the circuit according to FIG. 5 by the temperature correction circuit and to replace the variable delay circuit according to FIGS.

The circuits shown there replace the fixed delay the delay circuit 84 by a delay of variable length, the Duration of the difference between the temperature of the grains to be tested and the initial temperature of the temperature-sensitive element depends. In particular, the implementation of measurements by the moisture tester is delayed until the rate of change of the output signal of the temperature-sensitive element below a predetermined one Value falls.

A block diagram of the circuit for temperature correction and induction a variable delay is shown in Fig.9. The circuit contains an amplifier circuit 800 and a thermocouple 500 which is similar to that described above in connection with Fig.6 was described, which is at the input of the amplifier circuit and which generates a signal at an output terminal 802 which is of the Thermocouple determined temperature depends. The signal at output terminal 802 can be fed to an input of the clock generator 58 in FIG. The output signal of the amplifier 800 is also fed to the input of a differentiating circuit 804, which produces an output signal that is the time derivative of its input supplied signal corresponds. The output of the differentiating circuit 804 is amplified by an amplifier 806 and by a full wave rectifier 808 rectified. The full wave rectifier ensures that the delay circuit for positive and negative changes in the output signal of the thermocouple responds in the same way. The output of the full wave rectifier is connected to a driver 810, which is dependent on the amplitude of the rectifier output signal provides a bimodal output signal. The output signal of the driver 810 is used the actuation of a temperature gate. The temperature gate is between the Flip-flop 80 and the clock 58 and prevents the activation of the clock through the flip-flop as long as the temperature gate is not set. The temperature gate but is only set when the rate of change of the output signal of the Thermocouple 500 falls below a predetermined value.

FIG. 10 shows a schematic circuit diagram of the block diagram according to FIG Fig. 9. The constantan side of thermocouple 500 is with the positive input an operational amplifier 820 operating as a differential amplifier is connected. the Chromel side of the thermocouple is first connected to the second via a resistor 822 positive voltage source V2 connected and secondly via the series connection of a fixed and one variable resistor 824 and 826 respectively with earth. The negative one The input of the operational amplifier 820 is connected to the output of the amplifier via the Parallel connection of a resistor 828 and a capacitor 830 connected. Of the negative input of this amplifier is also via a resistor 834 with a node 832 and via a resistor 836 with the second positive voltage source V2 connected. A diode 838, the anode of which is connected to the second positive voltage source V2 is present, connects it to circuit point 832. Resistor 840 connects node 832 to ground.

The output of the amplifier 820 is via a resistor 842 with connected to the collector of a pnp transistor 844. Emitter and base of this transistor are connected to one another via a resistor 846, the emitter also having the second positive voltage source V2 is connected, while the base further is connected to the collector of an npn transistor 848 through a resistor 850. The emitter of transistor 848 is connected to ground. The base of this transistor is connected to a node 852 via a resistor 854 and further through a resistor 858 to a node 856. The node 856 can either be connected to the second positive voltage source V2 or to ground be, by switching devices, which are shown schematically as a single-pole changeover switch 860 are shown. Node 856 can be connected to either the second positive Voltage source V2 or be connected to earth by switching means that are shown as single pole changeover switch 862.

In reality, the switching devices known as switches 860 are shown, the output 806 of the flip-flop 80 in Fig.3. The switching point A positive voltage is then supplied to 852 when the flip-flop 80 is in the "Emptying" state and when the test device is in "Balance" mode is working. On the other hand, node 852 is connected to ground when the flip-flop 80 is in the "fill" state and when the tester is in the "Display" mode is working. The switching devices by the switch 862 may be part of a circuit that includes the temperature correction circuit switches off when the test device is calibrated. Node 856 is located so normally on earth potential, but is brought to a positive voltage, while the calibration is taking place.

As can be seen from the description above, the Operational amplifier 820 as a direct current differential amplifier.

Resistor 828 serves as a feedback element and its resistance value determines the gain in connection with the input resistance of the amplifier same. Capacitor 830 is provided in the feedback loop to provide the To stabilize amplifier and to reduce its gain for high frequencies, thereby reducing the noise. The network which the resistors 834, 836 and 840 as well as the diode 838 is used for direct current shifting at the amplifier output. The change in the resistance of diode 838 with temperature is used to compensate the stresses caused by the connection of different metals at the connection points of the thermocouple generated with the remaining parts of the temperature correction circuit will. A variable resistor 826 can be used to control the temperature correction circuit to calibrate and to set the output of amplifier 820 to a specified value, when the thermocouple 500 is at a known temperature.

If the circuit points 852 and 856 are at the reference potential, the collector-emitter circuit of transistor 848 is relatively non-conductive. Consequently the collector-emitter circuit of transistor 844 is also non-conductive and on the output terminal 2 appears a signal which corresponds to the output signal of the amplifier 820 is proportional. If either node 852 or 856 is a positive Has potential, as this occurs when the test device is in the "Balance" operating mode is working or being calibrated, the emitter-base junction of transistor 848 in Forward biased so the emitter-collector circuit of this transistor becomes conductive. A current then flows through resistor 850, which is sufficient is large in order to control the emitter-base junction of the transistor 844 conductive, so that the emitter-collector circuit of this transistor conductive and the output terminal 802 to the voltage supplied by the voltage source V2 holds, whereby the correction circuit is switched off.

The output of amplifier 820 is through the series connection one Resistor 870 and a capacitor 872 to the negative input of an operational amplifier 874 connected, which works as a differential amplifier. The capacitor 872 and the relatively low input impedance at the negative input of the operational amplifier 874 together form a differentiating circuit.

The positive input of op amp 874 is through a Resistor 876 connected to the second positive voltage source V2. The exit of amplifier 874 is connected to its negative input via a feedback branch connected, which is the parallel connection of a resistor 878 and a capacitor 880, these components having a similar function to the corresponding ones Components that are connected to the operational amplifier 820. The outcome of the Operational amplifier 874 is also connected to the two nodes via diodes 886 and 888 882 and 884 connected, the diodes being oppositely polarized. The diodes 886, 888, 890 and 892 form a common full-wave rectifier whose output lies between nodes 882 and 884. As a full wave rectifier a full-wave rectifier that contains two pnp transistors, whose Collectors are connected to earth via a common load resistor, whereby the base of the first and the emitter of the second transistor to the output of the Amplifier 874 are connected and the emitter of the first and the base of the second Transistor are connected to the second positive voltage source V2.

A resistor 894 lies between nodes 882 and 884. The node 884 is also connected to the base of a through a resistor 896 npn transistor 898 connected, its Emitter with the node 882 and its collector via a resistor 900 to the first positive voltage source V1 is connected, which has a higher positive voltage than the voltage source V2. The transistor 298 and the associated components amplify the output signal of the full wave rectifier and work as drivers.

When the temperature of the thermocouple 500 has stabilized or only changes relatively slowly, the output signal 820 is relatively stahil.Dem A low input signal is applied to the negative input of amplifier 874 and the output of amplifier 874 becomes about the potential of the second positive voltage source V2 held. This results in between the circuit points 882 and 884 a relatively low signal level, which is no longer sufficient, the base-emitter path of transistor 898 and thus the emitter-collector circuit to keep this transistor conductive. The collector of transistor 898 then remains about the voltage of the first positive voltage source V1. However, if the temperature detected by the thermocouple 500 changes relatively quickly, changes the output of amplifier 820 also turns out to be relatively fast and negative A relatively high input signal is applied to the input of amplifier 874. That Output of amplifier 874 then softens on the voltage of the second positive voltage source V2 by a relatively large amount. As a consequence, that there is a relatively high signal level between points 882 and 884, which is sufficient to positively bias the base-emitter junction of transistor 898 so that the Emitter-collector circuit of this transistor conducts. The collector of the transistor 898 then receives approximately the voltage of the second positive voltage source V2. When transistor 898 and associated components are chosen such that only a relative small change in base-emitter current required is to change the emitter-collector circuit from a relatively non-conductive to a nearly to transfer fully conductive state, the output signal at the collector is this Transitors essentially bimodal, depending on the rate of change the temperature determined by the thermocouple 500.

The collector of transistor 898 is connected through a resistor 902 connected to the base of an npn transistor 904. The base of this transistor is furthermore via the series connection of a capacitor 906 and a resistor 908 connected to a node 910. The circuit point 910 can either with the second positive voltage source V2 or connected to ground, namely via switching devices, shown schematically as a single-pole changeover switch 912 are.

The switching devices represented by switch 912 can in reality be the output 86 of the flip-flop 80 in FIG. As with the switch 860, a positive voltage is applied to node 910 when the Flip-flop 80 is in the "drain" state and when the tester is in the operating mode "Balance" works. On the other hand, the node 910 is connected to ground if the Flip-flop 80 is in the "fill" state and when the tester is in the "Display" operating mode is working.

The emitter of transistor 904 is connected to the second positive voltage source V2 is connected and its collector is connected to the first positive voltage source V1 connected through a resistor 914. The transistor 904 and its associated components work as a temperature gate switch. The output signal is from an output glue 916 tapped, which is connected to the collector of transistor 904 and fed from there to the clock generator 58.

When the collector of transistor 90 is at the potential of the first positive voltage source is V1, as is the case when the thermocouple 500 has reached a relatively stable temperature, the transistor 904 is conductive and the output terminal 916 is at the potential of the second positive voltage source V2. When the flip-flop 80 changes from the "emptying" state to the "filling" state, the potential at node 910 drops from that of the second positive Voltage source V2 at ground potential and the base Es transistor 904 becomes a negative Pulse supplied, the duration of which depends on the resistance values of the resistors 900, 902 and 908 as well as on the capacitance of the capacitor 906 depends. The transistor 904 is then blocked and a positive pulse appears at output terminal 916. The negative voltage jump of this pulse, i.e. its trailing edge, can be used to trigger the clock 58 in FIG.

When the collector of transistor 898 is at the potential of the second positive voltage source V2 is, as is the case when the thermocouple 500 has not yet reached a stable temperature, transistor 904 is non-conductive and the potential at the output terminal 916 is equal to the potential of the first positive voltage source V1. A change in the potential of the second positive voltage source V1 at ground potential then has no negative voltage change at the output terminal 916 result. However, when the thermocouple 500 is in a relatively stable state reached, the voltage at the collector of transistor 898 changes to that the first positive voltage source V1, whereby the transistor 904 becomes conductive and whereby a negative voltage change occurs at the output terminal 916. This negative voltage change is in turn used to trigger the clock 58 in FIG Fig. 3 used.

It can therefore be seen that in connection with the present invention a Frequency measurement circuit was developed in which the relationship between the output signal and the frequency of the input signal as a function of a number of different ones Input parameters can be changed easily. In particular, the The above description of a moisture tester for grains, its output signal can be evaluated in a simple manner, which can be evaluated by the user in a simple manner for measuring the moisture content of a wide variety of different Types of grains can be set, which for a compensation of temperature differences ensures in the temperature of the grains to be tested and what changes the operating parameters its electrical circuits are automatically compensated. In addition, the moisture testing device according to the invention delays the display for a time be determined by the difference between the temperature of the grains to be tested and the initial temperature of a temperature-sensitive element depends. Furthermore It goes without saying that numerous changes are made to the exemplary embodiments discussed are possible without deviating from the basic idea of the invention. This is how it is, for example possible to change details of the circuits within wide limits. Furthermore is it is possible to add the logical links between the individual circuits change. It is also possible to create a cell for the grains to be tested, which has a different shape than the one shown and it is finally possible to use the considered circuits to be supplemented by additional circuits in order to opposite the approximate solutions discussed here to achieve even more precise measurement results.

Claims (25)

Claims Device for determining a physical parameter, which is associated with a electrical variable linked in a predetermined, in particular variable manner is, in particular a moisture tester, preferably for grains, characterized in, that means for generating first electrical signals of predetermined length are provided that control devices for electrical control of the length of the first signals are provided that means for generating a second signal are provided with a frequency proportional to the electrical quantity and that Display devices are provided which show the number of oscillations of the second Show signal for the duration of a first signal. 2. Apparatus according to claim 1, characterized in that the devices for generating the first electrical signals as a periodically controlled clock are trained. 3. Apparatus according to claim 1 and 2, characterized in that with the Display devices connected to compensation devices are the the means for generating the first electrical signals of predetermined length control so that the predetermined length is set so that at the end of a first signal results in a predetermined counter reading in the display devices and that devices are provided to the compensation devices and turn off. 4. Device according to claim 1 to 3, in particular for measuring an impedance, in a known but variable manner with a physical parameter is linked, characterized in that a clock generator for generating a characteristic, electrical signal of predetermined length is provided that control devices for electrical control of the predetermined length are provided that an oscillator is provided that contains the impedance as a frequency-determining element that with the oscillator and the clock display devices are connected to this serve, the number of oscillations of the oscillator during an electrical signal to determine a given length and to provide a direct indication, and that with the control devices means for changing the predetermined length as a function of of the changes in the relationship between the measured impedance and the physical Parameters are connected. 5. Apparatus according to claim 1, in particular for testing the moisture content of a material to be tested by measurement one of the electric Properties of this material, characterized in that a cell for receiving an amount of the material to be tested is provided that an oscillator is provided is that this cell contains as a frequency-determining element that facilities are provided for generating an electrical signal, which has a predetermined period That means to display the number of times that the oscillator has during duration This period generated vibrations are provided and -that devices for Control of the length of the period are provided. 6. Apparatus according to claim 5, characterized in that devices are provided to the means for generating the signal with a period predetermined duration to cause this signal of predetermined duration to periodically generate that with the display devices and the control devices for setting the duration of the predetermined period compensating devices are connected to on End of the signal to receive a predetermined display of the display devices and in this way to obtain a reference operating condition for the device, and that Facilities are provided to either turn the balancing devices on or off turn off. 7. Apparatus according to claim 5, characterized in that devices are provided to measure the moisture content of various materials with a Variety of relationships between the moisture content and to measure the measured electrical property, and that with the facilities to control the period material selectors are connected to the period in accordance with the nature of the special relationship between the moisture content and the measured electrical property for the particular material under test are provided. 8. Apparatus according to claim 7, characterized in that the material selection means of slope selectors for changing the period in accordance with the slope of a linear approximation function for the particular relationship between the moisture content and measured electrical property for the test Material. 9. Apparatus according to claim 7, characterized in that the material selection means of intersection selectors for changing the period in accordance with the intersection of a linear approximation function of the special relationship between the moisture content and the measured electrical property of the test Material. lo. Device according to claim 7, characterized in that non-linear Correction means are provided for changing the period by an amount that is linked to the operating frequency of the oscillator. 1X. Apparatus according to claim 10, characterized in that the material selection means of curvature selectors for adjusting the magnitude of the period change that is created by the non-linear correction devices. 12. Apparatus according to claim 1, in particular moisture tester for Determining the moisture content of the grains to be tested by measuring the dielectric constant these grains, characterized by having a capacitive cell for receiving a set of the grains to be tested is provided that an oscillator is provided is that this cell contains as a frequency-determining element that a clock is provided, which generates an electrical signal which has a predetermined period Duration has that with the output of the clock generator and the oscillator a gate circuit which is the output of the oscillator only during the presence a clock signal lets through that counting devices are provided, which with connected to the output of the gate circuit and serve to set the number of oscillations of the oscillator which occur during a clock signal, and that control devices are provided, which the duration of the signals of the clock steer. 13. Apparatus according to claim 12, characterized in that return devices are provided to the clock periodically excite that with the counter and the control devices are connected to compensation devices which at the end of each clock period depending on that of the counters set the clock period so that at the end of each Clock period gives a predetermined display and that facilities are provided are to switch the compensation devices on or off. 14. Apparatus according to claim 12, characterized in that with the control devices Selectors are connected to the period in accordance with nature the special relationships between moisture content and dielectric constant for the grains to be tested. 15. Apparatus according to claim 14, characterized in that the material selection means consist of intersection selectors that serve to set the period accordingly the intersection of a linear approximation function for the particular relationship between the moisture content and dielectric constant for the material under test to change. 16. Apparatus according to claim 14, characterized in that non-linear Correction devices are provided with the control devices for the Period are connected and serve to increase the period in a measure change, which is linked to the operating frequency of the oscillator. 17. Apparatus according to claim 16, characterized in that the grain selection means formed by curvature selectors which serve to select the size the change in period caused by the non-linear correction devices will discontinue. 18. Apparatus according to claim 12, characterized in that temperature correction devices are provided, which are connected to the control devices for the clock period and serve to change this period to an extent which is proportional to the temperature the grain to be tested is linked. 19. Apparatus according to claim 14, characterized in that the temperature correction devices include a ribbon-shaped thermocouple in the capacitive cell and that it is with connected to the clock to change the duration of the period. 20. Apparatus according to claim 1, in particular moisture test for Generating a direct indication of the moisture content of the grains to be tested by measuring the dielectric constant of these grains, which is suitable the moisture content of a variety of different types of grains with different Relationships between the moisture content and the dielectric constant to measure, characterized in that a capacitive cell for receiving a Number of grains to be tested is provided that an oscillator is provided, which contains the cell as a frequency-determining element that a clock generator for generation an electrical signal is provided with a period of predetermined duration, that a gate circuit is connected to the output of the clock generator and the oscillator which is the output signal of the oscillator only during the presence of the clock signal lets through that counting devices are connected to the output of the gate circuit, which is the number of times the oscillator oscillates during the clock signal indicate that control means are used to control the signal period of the clock it is provided that feedback devices for periodically exciting the clock it is provided that with the counting devices and the control devices compensating devices are connected, depending on the counters at the end of the clock period set the clock period in such a way that at the end of each clock pulse a predetermined display is achieved that facilities for switching on and off the compensation devices are provided that with the control devices for Control of the period of the clock generator connected to temperature correction devices are to change the period by an amount commensurate with the temperature of the test Grain is linked to that with the control devices non-linear Correction devices are connected to change the period by an amount which is linked to the operating frequency of the oscillator, and that with the control devices Selectors are connected, which slope selectors for the Change of period in accordance with the slope of a linear approximation function for the special relationship between moisture content and dielectric constant for the grains to be tested, which further comprise intersection selection means to change the period depending on the size of the period change, which of the non-linear correction devices depending on the size the deviation of the special relationship between the moisture content and the Dielectric constants were brought about by the linear approximation function. 21. Device for determining the moisture content of an in das.Gerät introduced amount of grains, in particular according to one or more of the preceding Claims, characterized in that devices for performing a measurement a physical property of the grains are provided that facilities for sensing the temperature of the grains that means for changing it are provided the measurement as a function of the output signal of the temperature sensing devices are provided and that facilities for delaying the implementation of the measurement to be provided with a period starting with the difference between the temperature of the grains and that measured by the temperature sensing devices was established before the grains were entered into the device is linked. 22. Device for determining the moisture content of an amount of to testing grains, in particular according to one or more of claims 1 to 20, characterized in that means for performing a measurement of a physical size of the grains are provided that facilities for scanning the temperature of the grains are provided that facilities for changing the measurement depending on the output signal-r temperature sensing devices are provided and that delay devices are provided to enable the measurement to be carried out delay until the rate of change of the output signal of the temperature sensing devices falls below a predetermined value. 23. Moisture testing device, especially after one or more of the preceding claims, characterized in that a capacitive cell to accommodate a number of grains to be tested is provided that an oscillator is provided, which contains the capacitive cell as a frequency-determining element, that a frequency process circuit is provided which supplies an output signal, which is linked to the moisture content of the grains, that a temperature sensor is provided which the temperature the grain scans and connected to the frequency measuring circuit that with the output of the temperature sensor a differentiating circuit is connected, that a control circuit is provided, which has an output which is connected to the frequency measuring circuit and to it serves to switch on the frequency measuring circuit, and that a threshold value circuit is provided, which lies between the control circuit and the differentiating circuit and prevents the frequency measuring circuit from working as long as the output signal the differentiating circuit exceeds a predetermined value. 24. Moisture measuring device according to claim 23, characterized in that that a full-wave rectifier is provided, which is connected to the output of the differentiating circuit is connected, and that the threshold value circuit contains a gate circuit, which connected to the output of the full wave rectifier and between the control circuit and the frequency measurement circuit is located. 25. Moisture meter according to claim 24, characterized in that that the control circuit contains manually operable switching devices that serve that the signal at the output of the control circuit is changed.