JPS5995450A - Measurement device for moisture content - Google Patents

Abstract

PURPOSE:To obtain a measurement device which compensates the error occurring in the bulk density and temp. of an object to be measured itself and the error occurring in the temp. drift of oscillation circuits by disposing a pair of electrodes in the object to be detected and measuring the moisture content of said object from the dielectric contant between the electrodes. CONSTITUTION:A resonance circuit 1 makes the common use of the oscillation section of oscillation circuits, 2, 3. The circuits 2, 3 output time-dividedly an oscillation frequency f1 which is relatively at a high frequency and an oscillation frequency f2 which is relatively at a low frequency while the circuits are alternately switched and driven respectively at times tauH and tauL. The high frequency signal fH and the low frequency signal fL are subjected to a voltage to current conversion in V-I converters 24, 34, and are put in a transmission line 5 via capacitors C3, C4; further the signals are demodulated to the original signals fH, fL by a filter 9. The frequency calculated from the set values in registers 16, 17 and the switching time by envelope signals is determined. The count value correlating to the temp. of the grain detected by a thermistor 4a is stored in the register 42 and the count value correlating to the temp. in the oscillation section detected by a thermistor 4b is stored in the register 45. A microcomputer 18 calculates the moisture content from the frequency including the change in the bulk density and the temp. of the grain stored beforehand therein and the temp. in the oscillation circuit section.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a moisture content measuring device in which a pair of electrodes are arranged inside the subject, and the moisture content of a subject such as grain is measured by the dielectric constant between the electrodes. This applies particularly to a moisture content measuring device that compensates for errors based on the bulk density and temperature of the sample and the temperature of the oscillation circuit.

As a device for measuring the moisture content of grains, etc. by compensating for errors based on bulk density, for example, two pairs of electrodes are placed inside the grain, and two oscillation circuits each using an oscillation capacitor are used to measure the moisture content of grains. There is one that oscillates different frequencies and calculates the moisture content from the ratio of each oscillation frequency.

In this device, the moisture content is proportional to the dielectric constant between the electrodes, and therefore the oscillation frequency, and the bulk density is proportional to the ratio of changes in two types of oscillation frequencies (relatively at high frequencies). (This is because the frequency change becomes large relative to the change in bulk density.) Moisture content is measured based on two types of oscillation frequencies when grains with the same bulk density are sandwiched between electrodes. This is how it was done.

However, the above measuring device requires two sets of electrodes, and the bulk density between the electrodes is not necessarily the same, which complicates the configuration of the measuring section and makes accurate moisture content measurement difficult. There are no drawbacks.

In order to eliminate the above-mentioned drawbacks and further improve the accuracy of moisture content measurement, the present invention provides a moisture content measuring device that compensates for errors based on the temperature of the subject itself and errors based on the temperature drift of the oscillation circuit. With the goal.

This invention can be summarized as follows.

A pair of electrodes is placed inside the subject, and these electrodes are used as a shared oscillation capacitor for H1! The IT oscillation circuit oscillates two types of frequencies. At this time, the driving of the two oscillation circuits is
This is done alternately using a switching circuit. In addition to the electrodes, a subject temperature sensor is provided within the subject to measure the temperature of the subject itself, and an oscillation section temperature detection sensor is further provided to detect the temperature of the oscillation circuit section. Then, the switching time for one of the oscillation circuits of the switching circuits is changed in accordance with the output of the object temperature detection sensor, and the switching time for the other oscillation circuit is changed in accordance with the output of the oscillation section temperature detection sensor. The outputs of the respective oscillation circuits are superimposed and sent to the transmission line, and on the receiving side, the original oscillation output is obtained by a filter. Since the 47th oscillation output itself has switching time information, the frequency can be determined by counting the number of oscillations within the switching time. Further, the temperature of the object can be determined from the switching time information of one of the oscillation circuits alone. Furthermore, the temperature of the oscillation circuit is determined from the switching time information of the other oscillation circuit alone. The microcomputer, which is the calculation means, performs these calculations, and then multiplies the obtained frequency by the coefficient of variation for each temperature drift of the bulk density change 1 oscillation part to obtain a new frequency, and then calculates the new frequency based on this new frequency. to find the moisture content. Note that the coefficients of variation of the two types of frequencies with respect to changes in bulk density and the coefficients of variation of the two types of frequencies with respect to the temperature drift of the oscillation section are stored in advance in the microcomputer.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a grain moisture content measuring apparatus according to an embodiment of the present invention.

In the same figure, the upper and lower electrodes of a capacitor C1 (oscillation capacitor) are placed in a hole in which grains are stored.

Capacitor C2 and coil L connected to capacitor CI
L and L2 constitute a resonant circuit 1 together with a capacitor C2. The resonance circuit 1 constitutes an oscillation section of a first oscillation circuit 2 and a second oscillation circuit 3. The oscillation drive section of the first oscillation circuit 2 includes an amplifier 201 having a positive feed hack loop.
A detection circuit 21 that detects the oscillation output. A comparator circuit 22 that compares a switch-no-ang signal τH, which will be described later, with the output of the detection circuit 21. It is composed of an amplifier 23 that controls the driving time of the amplifier 20 by setting the comparison output to a predetermined level. Also, the second
Similar to the first oscillation circuit 2, the oscillation driving section of the oscillation circuit 3 includes an amplifier 30. It is composed of a detection circuit 31, a comparison circuit 32, and an amplifier 33.

The reactance of the coil L1 of the resonant circuit 1 is set to be much larger than the reactance of the coil L2. Therefore, the oscillation frequency 11 of the first oscillation circuit 2 is 1/(2π L2CIC2/ (CI + C2)), and the oscillation frequency f2 of the second oscillation circuit 3 is 1/(2π L2CIC2/ (CI + C2)).
l (C], +C2)).

That is, the resonant circuit 1 serves as the resonant parts of two oscillation circuits, and causes the first oscillation circuit to oscillate a relatively high frequency, and causes the second oscillation circuit to oscillate a relatively low frequency.

The two oscillation circuits 2 and 3 are alternately switched and driven by a multi-by-break 4 constituting a switching circuit. This multi-pipe lake 4 has two CR time constant circuits (not shown) for determining the switching period, and the R section of one of the time constant circuits is composed of a thermistor 4a placed inside the hopper. has been done. Further, the R section of the other time constant circuit is composed of a thermistor 4b arranged on the oscillation circuit board. Of both stage outputs of the multi-pipe lake 4, the stage output affected by the thermistor 4a is given as τH to the comparison input terminal of the comparison circuit 22, and the stage output affected by the thermistor 4b is given as τL for comparison. It is applied to a comparison input terminal of circuit 32. That is, the stage output τH1τ
As for L, the multi-by-break 4 constitutes a temperature one-hour converter. As mentioned above, the comparator circuit 22. '32 compares the signal τH2τL with the output of the detection circuit 21.31, but outputs a comparison output only when the levels of both are the same. Therefore, the oscillation circuits 2 and 3 each have τH2τL
The oscillation frequency fl, which is a relatively high frequency, and the oscillation frequency f2, which is a relatively low frequency, are outputted in a time-division manner while being alternately switched and driven during times of.

High frequency signal fH (oscillation frequency fl) and low frequency signal f
L (oscillation frequency f2) is voltage-current converted by V-1 converter 24.34, and capacitor C3 and capacitor C
4 and onto the transmission line 5. The transmission line 5 is composed of a coaxial cable, and also serves as a power supply line for supplying voltage to the oscillation circuits 2 and 3. That is, the transmission line 5 simultaneously supplies voltage to the oscillation circuit 2.3 and transmits two oscillation signals. Since the power supply voltage and two oscillation signals are superimposed on one line in this way, the filter 6 is provided to extract only the power supply voltage from the transmission line. A constant voltage power supply circuit 7 connected to the filter 6 is provided to stabilize oscillation and prevent measurement errors.

A power source E for supplying voltage to the oscillation circuit 2.3 and a capacitor C5 for extracting only the signal are connected to the receiving side of the transmission line 5.

The canted DC signal is made to an appropriate level by an amplifier 8, and is further converted to the original high frequency signal f by a filter 9.
It is demodulated into H and low frequency signal fL.

Each demodulated signal is sent to an envelope detection circuit 10.11.
The signal is then guided to the counters 12, 1'3, and an envelope delayed signal obtained by delaying the envelope signal by a delay circuit 14.15 is guided to the positive terminals of the counters 12, 13.

The counters 12 and 13 count the high frequency signal fH and the low frequency signal fL while repeatedly being reset at the falling edge of the envelope delay signal. Therefore counter 12
, 13 are respectively switching times τH.

The results of counting the signals fH and fL during τL are held. The registers 16' and 17 latch the contents stored in the counters 12 and 13 at the falling timing of the envelope delay signal, and output the contents to the microcomputer 18, which is an arithmetic means. , is a signal waveform diagram of the main part of the lJ constant device. As shown in the figure, the high frequency signal fH is generated only when the signal τH is high, and the low frequency signal fL is generated only when the signal τL is low. Therefore, by counting the number of oscillations when the signal τH2τL is high, the frequencies of the signals fH and fL can be found. The microcomputer 18 has register 1
As a first calculation, the frequency is determined from the value set at 6.17 and the Sui-7 amplifier time obtained from the envelope signal.

On the other hand, the high frequency signal fH among the demodulated signals described above is also input to the envelope detection circuit 40, and the valid time of the switching signal τH and the falling timing of the signal are detected. Time for the former.

That is, the high frequency switching time is used as the operating time of the counter 41 which uses a constant clock as an input pulse. The latter falling timing is used as a launch signal for setting the value set in the counter 41 in the register 42. Therefore, register 42
A count value correlated to the temperature of the grain detected by the thermistor 4a is stored, and the microcomputer 18 determines the grain temperature from the count value based on a predetermined correlation coefficient.

Similarly, the low frequency signal fL is also input to the envelope circuit 43, and the valid time of the switching signal τL and the falling timing of the signal are detected. Then, during the valid period of the former signal, a constant input pulse is counted by the counter 44, and the counter value is launched into the register 45 by the latter signal. Therefore, the register 45 stores a counter value that correlates with the temperature of the oscillation circuit section detected by the thermistor 4b, and the microcomputer 18 calculates the temperature of the oscillation circuit section from the counter value based on a predetermined correlation coefficient. .

After determining the frequency, grain temperature, and oscillation circuit temperature in this way, calculations are then performed to determine the moisture content.

This calculation calculates the frequency variation coefficient for changes in bulk density as a
(High frequency variation coefficient of about IOMH2).

b (low frequency coefficient of variation of about IMH2), c and d are the frequency variation coefficients with respect to changes in grain temperature, and e and f are frequency variation coefficients with respect to temperature drift of the oscillation circuit section, and execute the following formula. . Note that these coefficients are stored in advance in the microcomputer 18.

p (moisture content) = (a-c-e-fH)/(b-d-f-fL) As described above, in this embodiment, the high frequency and low frequency oscillation circuits are alternately operated using the same oscillation capacitor. The frequency is determined by counting the number of oscillations in the driving poem, and then the moisture content is determined from that frequency. Normally, the switching time for alternately driving the oscillation circuits 2.3 is set to be very short with respect to the movement of the grain that is the subject. This allows both high and low frequencies to be measured when the grain condition is fixed. That is, only one set of electrodes is used, but two different frequencies are measured under the same conditions. Therefore, the measuring section becomes simple and measurement errors do not occur. Furthermore, the oscillation circuit 2.
Since the voltage supply to 3 and the transmission of the oscillation signal are performed by one transmission line, there is an advantage that the wiring is simple.

Furthermore, since the grain temperature information is obtained at the pulse interval of the switching signal τH, and the temperature information of the oscillation circuit section is obtained at the pulse interval of the switching signal τL, a separate transmission line for transmitting the temperature information is required. It has the advantage of not being necessary.

In the above embodiment, the transmission line 5 is also used for voltage supply, but the transmission line 5 may be used exclusively for oscillation signals and a separate power supply line may be provided.

As described above, according to the present invention, the oscillation capacitor is
Since only one electrode is used, the configuration of the measurement unit is simplified, and there is no need to make any efforts to arrange the electrodes inside the subject.
Changes in the electrode over time affect both oscillation frequencies by the same rate, which has the effect of reducing errors caused by changes in the electrode portion over time. Furthermore, since the temperature information of the object and the temperature information of the oscillation circuit section are transmitted in the switching time, there is no need to take noise countermeasures as in the case of transmission at the voltage level. This has the effect of simplifying the configuration of the transmission section and maintaining high accuracy even if the transmission line becomes long.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a grain moisture content measuring apparatus according to an embodiment of the present invention. FIG. 2 is a signal waveform diagram of the main parts of the same device as shown in FIG. 1-resonant circuit, 2-first oscillation circuit, 3-second oscillation circuit, 4-multi-no-e break (switching circuit),
4a-thermistor (subject temperature detection sensor), 4b-thermistor (oscillation circuit temperature detection sensor), 5H transmission line, 9-filter ((for K KEI), 18-microcomputer, C1-Q[ii capacitor. Application Person: Kubota Iron Works Co., Ltd. Agent, Patent Attorney, Ketsuo Komori (Figure 1, Figure 1, 1112, Procedural child l ↑ Self-directed) January 10, 1981, Director General of the Agency, Mr. Akira, Name of Person Who Corrects a Moisture Content Measuring Device Incident Related Patent Applicant Address 1-2-47 Shikitsuzuka, Naniwa-ku, Osaka Name (1
05) Kubota Iron Works Co., Ltd. Representative Shigekazu Mino 7 people 1 location Q543 1-14-2 Shitennoji, Tennoji-ku, Osaka City
No. 2 Nissin Building No. 702 Increasing number of inventions by King None Volume 8 of "Detailed Description of the Invention" in the subject specification of King Contents of amendment (1) rl/ (2π) on page 6, line 13 of the specification L2CIC2/ (CI+C2))
'1/(2π L'2CIC2/(CI+C2)),
Correct with T. (2) rl '1/(2yr T, 1 (CI+C2))J on page 6, line 16 of the specification
/(2πVπ1 (Cd”C2))J.

Claims (1)

[Claims] (1) A pair of electrodes placed inside the subject, an oscillation circuit with two types of frequencies that configures an oscillation capacitor using these electrodes, a subject temperature detection sensor that detects the temperature of the subject, and the oscillation circuit. an oscillator temperature detection sensor that detects temperature;
The oscillation circuits are alternately switched and driven, and the switching drive time of one of the oscillation circuits is changed according to the output of the object temperature detection sensor, and the switching drive time of one of the oscillation circuits is changed according to the output of the oscillation section temperature detection sensor. a switching circuit that changes the switching drive time of the other oscillation circuit; a means for superimposing and transmitting the two outputs of the oscillation circuit; a filter means for demodulating the received signal after transmission into the original oscillation output; and a demodulated oscillation circuit. Determine the above two types of frequencies from the output and switching time, and determine the temperature of the object from the switching time of one of the oscillation circuits,
Also, determine the temperature of the oscillation circuit from the switching time of the other oscillation circuit, and determine the moisture content based on those values? ! A moisture content measuring device comprising: a 4-calculation means.