DE2847411C2 - Circuit arrangement of a vibration level measuring and display device - Google Patents

Description

marked by

c) a feedback circuit composed of one connected to the output of the amplifier (3) Voltage amplitude limiter (5) and a Differentiator (6), the output of which is sent to a frequency-setting RC element (19, 20) of the Shock excitation vibration generator (2) acts.

25th

The present invention relates to a circuit arrangement of a Vibrationsfüllstandsmeß- and display device for pourable and viscous goods with a mechanical vibration system and an electrical-mechanical vibration converter, which is electrically connected to the output ei? = £ s shock excitation vibration generator and the input of an amplifier is connected, its output to a display device connected

Such a circuit arrangement is known from US-PS 40 08 613. It is about the detection of the Level of the material to be measured in bunkers, cisterns, tanks or similar storage containers, namely in different Branches of production.

From DE-AS 17 73 815 a vibration level measuring device is known whose mechanical vibration system (tuning fork) on one of the inner Side wall of the container to be filled with the material to be measured is arranged. At the yoke of Tuning forks are piezoelectric transducers electrically coupled to one another by means of an amplifier In addition, a display device connected to the amplifier output is provided.

The first piezoelectric transducer sets the mechanical oscillation system in motion, while the second piezoelectric transducer (vibration sensor) controls the mechanical vibrations absorbs and converts it into a voltage proportional to its amplitude. This tension will then amplified by the amplifier and fed to the first piezoelectric transducer. Thus, the Vibrations with a natural frequency of the mechanical vibration system of the level sensor excited at a certain frequency.

When the mechanical vibration system is immersed in the material to be measured, its vibrations are dampened. The vibrations in the encoder are interrupted. so that at the output of the second piezoelectric Transducer no signal occurs. This becomes the display device de-energized and shows the filling of the Be

holder up to the level of the level sensor.

This known device is sensitive to interference caused by under industrial conditions usual vibrations, shocks, etc. are caused. Under the influence of such disturbances are wrong Triggering of the detector cannot be ruled out in the event that the sensor is showered with the material to be measured is and on its support body and thus-also on the piezoelectric transducer external vibrations or shocks are transmitted, in the spectrum of the natural frequency of the piezoelectric transducer and of the mechanical vibration system of the encoder are included.

Also must be the one that generates and absorbs vibrations Measuring transducers and the mechanical vibration system according to frequency in a wide temperature range must be strictly coordinated, since frequency changes of their oscillations to a corresponding one Change of the transfer factor of the detector and false triggering. This under Industrial conditions: it is extremely difficult to guarantee.

The piezoelectric transducer of the known device are arranged close to the material to be measured and subjected to its exposure to high temperatures, since the Curie temperature is of the piezoelectric material only 130 ⁰ C, IFER detector can not be operated at higher temperatures and is unsuitable for use in many branches of industry, for example. B. in the extraction of soda, cement and the like.

The same applies to one known from DE-AS 16 73 972 Vibration level measuring and display device, in which the mechanical vibration system in The form of a metallic membrane is formed, the vibrations of which on contact with the material to be measured be dampened.

From DE-AS 15 73 002 a Vibrationsfülistandsmeß- and display device is known in which the mechanical transducer is a rod supported by a AC power source is excited. This rod is suspended in a rubber-elastic disk which makes you feel strong damping factor of the mechanical vibrations. This strong damping is therefore necessary because it is difficult to set the oscillation-stimulating frequency of the supply generator with sufficient Accuracy to match the natural frequency of the mechanical system and to keep it there. Because this training in this known device of low sensitivity and accuracy and can only be used for heavy measuring goods, which a considerable damping when immersing the mechanism Effect Schwingers.

A vibration level measuring device known from SU Inventor's Certificate 2 62 418 has a rod-shaped one mechanical vibration generator and a device for generating vibrations that interacts with this as well as for converting the generated vibrations into electrical signals. This consists of two electrically coupled windings, which by means of a band amplifier with a frequency demodulator and a display device having an output gain stage.

One of the windings is used to excite the vibrations of the mechanical vibration system and is connected to the amplifier output; the other converts the mechanical vibrations into electrical ones um and is connected to the amplifier input. The windings thus form a positive return

3 4

coupling circuit of the amplifier and put together supply pulses are significantly larger than those for un-

with the encoder represents a self-excited oscillator. damped mechanical vibrations applicable decay

The amplification factor of the amplifier becomes untimely. This, in turn, allows the measurements to be adjusted only in the interrupted feedback loop so that significant time intervals, which reduce the vibration generation both without and with the measurement and display, are possible. Damping by the material to be measured is possible. The frequency control of rapidly changing levels is this frequency band, this amplifier covers the natural frequency and is therefore not very suitable,
quenzen de «mechanical oscillation system. The invention is based on the object of providing a gain; At the output, the frequency demodulator is quickly responding, with low energy consumption: «in which the voltage, which can be operated from the oscillator output, is de-converted in the direction of DC voltage changes for debris and viscous goods. The signal obtained is amplified in the ren reliability and operational safety independent output stage. If the mechanical oscillation of the natural frequency of the mechanical oscillation system is not immersed in the material to be measured, a high level of influence occurs in the system changing influences.
These vibrations with one of the natural frequencies 15 Starting from the generic design of the mechanical vibration system mentioned at the beginning, the task is solved Frequen.7, since even extremely small vibrations are caused by a feedback circuit from an external system as a result of fluctuations in the Supply voltage of the amplifier connected voltage or vibrations from construction elements- amplitude limiter and a differentiating element, whose th is amplified by the amplifier and fed into the oscillation system. j / irkt
the supply voltage can be fed in. Such a version of the vibration level indicator

The two windings are on the mechanical ders allowing the vibrations of the mechanical Oscillation system arranged. In doing so, they have to synchronize the oscillation system with its own oscillations and the; periodically triggering it with the line connecting the amplifier. Changes in ownership be mutually shielded. This complicates the frequency of the mechanical vibration system, which is in-Konstruktiou and reduces the reliability as a result of the material being measured sticking to the encoder,

Since the natural frequencies of the mechanical temperature fluctuations, aging of the encoder

system of this facility arise in the narrow band of material, etc., have no effect

200 to 400 Hz, there are 30 limits on the reliability of the operation for two-sided limitation,

of the pass range of the amplifier with uniform The invention is described below by the description

ger phase characteristic to introduce appropriate filters, exercise an exemplary embodiment on the basis of the drawing

what the same disadvantages entails, explained further; it shows

The construction-wise complicated device for F i g. 1 the functional diagram of the vibration filling

Stimulation of the mechanical vibrations and the 35 circumstance measuring and display device for rubble and vis-

turning deirseiben into electrical vibrations is in kose goods;

arranged in the vicinity of the material to be measured and its tempe- F i g. 2 schematically the level sensor;

rature, corrosion and other influences ex- F i g. 3 the block diagram of the vibration fairing

puts. This «laughs the application to control tors;

aggressive goods difficult. 40 fig. 4 shows the basic circuit diagram of the amplifier; Fig. 5

The invention is based on a circuit arrangement - the basic circuit diagram of the display device,
tion of a vibration level measurement and display device The vibration level measurement and display device with a pulse excitation of the mechanical device for debris and viscous goods has a level oscillations, as known from US-PS 40 08 613 encoder 1, which is connected to the output a shock excitation is. Here wiiiüd dar. Mechanical oscillation system 45 oscillation generator 2 and excited at the input of a coil which is connected by a pulse generator amplifier 3. The output of the gate is fed with short shock pulses. The same amplifier 3 is a display device 4 and a coil is used to convert the excited mechanical voltage amplitude limiter 5 connected. The see vibrations in electrical signals and is here- the output of the voltage amplitude limiter 5 is connected to the input of an amplifier, which acts 50 via a differentiating chain 6 on the shock excitation on a display device. Vibration generator 2 coupled.

Vibrations are generated abruptly during operation. The level sensor 1 has a mechanical vibration

and the indicated signal depends on the amplitude generation ^ system 7 from a rod 8, which is attached to one on one

and the duration of the subsequent damped support body 10 attached membrane 9 is attached.

Natural vibrations of the vibration system. Here 55 The level sensor ϊ also includes a vibration

a display can always be obtained that determines the transducer 11 both for moving the mechanical

will see from the degree of damping of the mechanical vibration system 7 in vibrations as well

Vibration system, which in turn goes from immersion to converting mechanical vibrations of the same

of the mechanical oscillator in the material to be measured. exercise in electrical vibrations. The vibration environment

The disadvantage of this design, however, is that the converter 11 consists of a winding 12 with a

not with the possibly still existing vibration non-ferromagnetic core 13 and acts both as an elec-

gen of the mechanical system synchronized shock magnet as well as a magnetic transmitter, which the

excitation impulses in phase opposition to these initiated vibrations of the mechanical vibration system

which, instead of stimulating it again, is converted to an alternating voltage of the appropriate frequency.

lead to a further attenuation of the same and a faulty 65 converts.

cause the display device to respond erratically The shock excitation oscillation generator 2 has a

would. To prevent this from happening, the thyristor 14 (FIG. 3) connected to the winding 12 must be connected to this plane

Known device, the pause between the excitation a discharge capacitor 15 is coupled. That

^{5 6} I.

The capacitor is charged via a Wi- voltage reaches the input of the display device J

derstand 16 from a supply source 17. The time-determined 4. i '|

Mende circuit of the oscillation generator 2 is of the type In the display device 4, this alternating voltage is i }.

an emitter follower with a transistor 18. rectified. The DC voltage is applied! |?

In the base circuit of the transistor 18, the electromagnetic control relay 41 is located by a 5, which by its j (j Resistor 19 and a storage capacitor 20 provide contacts 50 and 51 for the supply circuits of lamps 52

formed time-determining RC chain. The emitter circuit or 53 controls the presence or absence of \

of the emitter follower has the response threshold of the material to be measured at the setting level d ^ s mechani-::

Thyristor 14 determining Zener diode 21. A wi see oscillation system 7 signal. \ Ä

The stand 22 serves to limit the current of the transistor 10. The alternating voltage y amplified by the amplifier 3

18 at the time it was switched through. A resistor also reaches the voltage amplitude limiter 5, at ■ '*

23 together with the input resistance of the output forms an almost rectangular alternating voltage

Thyristor 14 the load on the emitter follower. A dilation arises. That at the output of the limiter 5 ^:

ode 24 is a differentiating element 6 connected to discharge the storage capacitor 20 differentiates these : · \

when the thyristor 14 responds. 15 pulses and generates 'ii' when the front flanks arrive

F i g. 3 also shows that from a resistor 25, one of the pulses synchronizing the square-wave voltage, each || Capacitor 26 and a diode 27 existing differences from those with the beginning of the Schwin-; ί

adornment 6. Periods of the mechanical oscillation system ^t?

The amplifier 3 corresponds to two transistors 28, 29 7

(F i g. 4) with direct couplings between the stages 20 The synchronized impulses release the oscillation

The DC operation of the amplifier is thus generated generator 2 in the times that

from an RC chain with resistors 30,31 and one strictly with the beginning of the natural period of the mechanical

Capacitor 32 guaranteed. Resistors 33, 34 see the oscillation system 7 match. Since the

nen as a burden in the reinforcement stages. The con- excitation impulses from the output of the oscillation gen-

capacitors 35, 36 are to separate the direct current 25 generator 2 on the with the mechanical oscillation system

couplings determined. A resistor 37 is used to arrive at anstems 7 interacting coil 12.

coupling of the differentiating element 6 via the span, the periodic

voltage amplitude limiter 5. This consists of a visual effect strictly in phase with the vibration

Stabilization element and acts as a maximum limitation of the mechanical oscillation system 7

zer the output voltage amplitude of the amplifier 30 and the vibrations are thus at their natural frequency

3. A capacitor 39 limits the effect of the frequency held.

amplifier 3 on low frequencies. If the transmitter 1 of the vibration level indicator is in ',

The in F i g. The display device 4 shown in FIG. 5 when the material being measured is immersed, the vibrations of the holds a transistor 40, in the collector circuit of which a mechanical oscillation system 7 is connected, a considerably geelectromagnetic relay 41. The relay 35 damps and is bridged by a capacitor 42 after the action of an exciter 41. In the emission pulse from the oscillation generator 2 to the system 7 terkreis the transistor 40 is a response threshold quickly decay.

the Zener diode 43 determining the display device 4. As a result, only the display device 4 reaches available. In the base circuit of the transistor 40 are very short-term excitation pulses, the diodes 44 and 45, which are used after the Mitein demodulator, as well as a 40 telung in the circle with the components 40, 41, 42, 44, 45, Capacitor 46 switched on with a resistor 47. 46 and 47 only one substantially below the response threshold of the transistor determined by the Zener-Der with a resistor 48 and a Zener diode 49 diode 43 designed circle is used to generate an output 40 lying DC voltage. The stream of the signals for contactless actuators. The transistor 40 is reduced, and the clektro relay 41 has contacts 50, 51, with the aid of which 45 magnetic relay 41 is switched off. Through the corresponding signal lamps 52 and 53 on or off contacts 50, 51 of the relay 41 is the corresponding be switched. Lamp switched on, which indicates that the material to be measured

The operation has reached the level measuring and setting height of the encoder described

-message device for rubble and viscous goods- changes in the natural frequency of the mechanical

runs as follows: 50 vibration system 7, which under operating conditions

The shock excitation vibration generator 2 generates as a result of a change in its mass, for. B. due to short-term impulses, the duration of which is possible for a significantly shorter material to be measured, or which are caused by and the cycle duration of which are several times greater than the changes in the ambient temperature or can be caused by the old natural period of the mechanical oscillation system. The values generated by the oscillation generator 2 will not have any effect on changes Short-term impulses reach the winding 12 and the excitation conditions of the oscillation system excite sudden vibrations in the mechanical, since in accordance with the frequency changes oscillation system 7. If this oscillate freely the oscillation system ments the temporal position of the can, its oscillations are changed during the time-synchronizing impulses is the perio- t between successive impulses span practical excitation of the vibrations of the mechanical table not damped vibration system 7 with the help of the vibration gen-

During the time span between the excitation stimulator 2, the oscillations of the mechanical gene frequency of the mechanical oscillation system are thus reliable with the actual egg pulses Oscillation system 7 recorded by the coil 12 synchronized, which increases the reliability and converted into an alternating voltage which results in the 65 and simplifies the design Input of the amplifier 3 is supplied. The amplifier 3 amplified by the encoder, one of its most susceptible components, with the natural frequency of the mechanism niche vibration system 7 alternating alternating

For this purpose 3 sheets of drawings

Claims (1)

Claim: Circuit arrangement of a vibration level measuring and display device for pourable and viscous goods a) with a mechanical vibration system (7) and an electrical-mechanical vibration converter (11), to b) the electrical with the output of a shock excitation vibration generator (2) and the input of an amplifier (3) is connected, the output of which is connected to a display device (4) is,