JPH0323875B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a signal transmission device between an ultrasonic acoustic sounding device disposed at a measurement location and an evaluation location distant from the measurement location, comprising: at least one ultrasound transducer, which is arranged at the measurement location, for transmitting ultrasound pulses in successive transmission periods and converting the echo pulses received after reflection at the target into electrical signals; a preelectronic device having an envelope generation circuit for generating an electrical envelope signal representative of the envelope of the echo signal, located at the evaluation point; and a connecting line for transmitting an envelope signal to the evaluation device, in which the envelope signal is evaluated in order to determine a target distance from the travel time of the ultrasonic pulse.

BACKGROUND OF THE INVENTION Devices of this type are often used for measuring the filling state in containers using ultrasonic acoustic sounding. For this purpose, an ultrasonic transducer is arranged above the maximum filling state occurring in the container, which transmits ultrasonic transmission pulses that reach the filling located in the container. The ultrasound echo pulses reflected at the filling are received by the same or a second ultrasound transducer and converted into electrical reception signals. From the travel time of the ultrasonic pulse, it is possible to calculate the distance from the ultrasonic transducer to the filling surface, and thus the filling state in the container. The excitation of the ultrasonic transducer for emitting ultrasonic pulses is carried out by electrical high-frequency pulses having an ultrasonic frequency.
These excitation pulses can have any desired pulse shape (envelope) and can be keyed to a rectangular shape, for example. The electrical reception signal sent out by the ultrasound transducer when receiving an echo pulse is
Although the high-frequency pulse has the same frequency, its curve shape is defined by the transfer function of the ultrasound transducer and the ultrasound propagation medium, and is different from the curve shape of the excitation pulse. Furthermore, the amplitude of the received signal is significantly smaller than the amplitude of the excitation pulse.

Particularly when using acoustic sounding devices to measure the filling state, it is often necessary to be able to use the measurement results at a location remote from the measurement location. On the one hand, the measuring points are often difficult to access for handling purposes and there are often unfavorable conditions there. On the other hand, it is desirable to collect the measurement results of a plurality of measurement points centrally.

#Siemens-zeitschrift〓42 (1968), Volume 1,
In the signal transmission device known from pages 18 to 22 in an ultrasonic sounding device used for filling level measurement, an electrical envelope signal representing the envelope of the echo pulse is generated in the front electronic device. is,
The envelope signal is then transmitted via a connecting line to a control and evaluation device that is separate from the front-end electronics.
In this way, the difficulties that arise with regard to the transmission of electrical high-frequency signals, especially when the transmission path has a relatively large length, are avoided, while on the other hand all important information of the echo pulses is preserved.
The reason is that this important information appears in the curved shape represented by the envelope. An envelope signal is a low frequency signal that can be transmitted through a customary laid cable of conductor of any length.

In order to obtain additional information and to increase the measurement accuracy and noise tolerance, it is often desirable to transmit further information from the measurement location to the evaluation location, characterizing the parameters occurring at the measurement location. Therefore, for example, the temperature of the ultrasonic propagation medium is important information for the accuracy of target distance measurement. This is because the propagation speed of ultrasound is temperature dependent and temperature is therefore relevant in calculating the distance traveled from the measured travel time. Ultrasonic acoustics for fishing purposes, with a measuring station attached to a trawl net, which is connected via a cable to an observation station attached to the ship's hull, as known from West German Patent Application No. 1915956 In depth sounding devices, a temperature sensor is installed at the measuring point, which generates a measured value signal representing the temperature of the propagation medium. The measured value signal is transmitted by the front electronics.
The time intervals from time zero of each transmission cycle are converted into processed echo pulses representing temperature measurements. The processed echo pulses preferably have the same carrier frequency as the true echo pulses and are transmitted together with the true echo pulses via the same cable to the observation station.

Problems to be Solved by the Invention In this known signal transmission device, processed echo pulses are also transmitted as high-frequency signals in addition to true echo pulses, which increases the problem of high-frequency signal transmission. This problem becomes even more severe when it is desired to transmit further parameter measurements from the measurement location to the observation station.

In contrast, the object of the present invention is to provide a further electrical signal in addition to the electrical envelope signal representing the envelope of the echo pulse, so that the transmission of the envelope signal is disturbed or has an interference effect. It is an object of the present invention to provide a signal transmission device in an ultrasonic sounding device, which can transmit signals between a measurement point and an evaluation point via the same connection line without receiving any interference.

Means for Solving the Problem This problem is solved by the invention in the following way in a signal transmission device of the type mentioned at the beginning.
That is, the generation and transmission of the envelope signal is performed in the first segment time of each transmission period, and
The duration of the segment time is at least equal to the longest possible transit time of an ultrasound pulse generated at the measurement location for the evaluation of the envelope signal in the second segment time of each transmission period. A low-frequency electrical signal, characterizing at least the temperature of the propagation medium of the ultrasonic pulse, is transmitted via the connecting line to the evaluation location, and at least one control signal is transmitted to the evaluation point via the connecting line, and at least one control signal is transmitted to the evaluation point at least one time interval of the respective transmission period. The control signals transmitted from the evaluation point to the measurement point via a connecting line are designed in such a way that they are in each case distinguishable from a low-frequency signal transmitted in the same time interval.

Effects of the Invention In addition to the envelope signal, all other signals are also transmitted at low frequencies in the device according to the invention, so that the advantages of low-frequency signal transmission remain intact. Particularly simple and inexpensive connecting lines of any length can be used. By transmitting the envelope signal in a separate time segment of the transmission cycle from other signals, any interference or disturbance of the envelope signal by other signals is avoided. It is therefore possible without any problem to transmit a plurality of low-frequency signals representing different parameters from the measurement location to the evaluation location and, in addition, to transmit control signals from the evaluation location to the measurement location. By this means, in particular, certain functions in the front-end electronics can be controlled from the evaluation point. For example, the amplification of the amplifier in the front-end electronics can be set from the evaluation point.

Advantageous embodiments of the invention are described in the subclaims.

Embodiments Next, the present invention will be described in detail with reference to the drawings, with reference to the illustrated embodiments.

FIG. 1 shows a container 10 placed at a measurement point M.
shows. A filling material 11 is contained in the container.
In order to measure the filling in the container 10, an ultrasonic transducer 12 is arranged on the upper side of the container above the maximum filling that occurs. The ultrasonic transducer periodically lowers the filling 1 in the container.
1, and receives the ultrasound echo pulses reflected at the surface of the filling 11 and converts them into electrical reception signals. The transit time of an ultrasonic pulse from the ultrasonic transducer 12 to the surface of the filling 11 and from there back to the ultrasonic transducer 12 is, at known propagation velocities of the ultrasonic waves, relative to the distance traveled by the ultrasonic waves within the container. It is a measure and therefore also a measure of the filling condition in the container. The propagation speed of the ultrasound waves depends in particular on the temperature of the propagation medium, which in the illustrated example is air above the filling in the container. In order to be able to take account of the influence of temperature on the propagation speed, a temperature detector 13 is provided within the container which delivers an electrical output signal that is dependent on the temperature within the container.

The ultrasonic transducer 12 and the temperature sensor 13 are connected to a front electronic device 14 which is also arranged at the measuring point M in the immediate vicinity of the container 10 .
Front-end electronics 14 sends electrical high frequency transmit pulses to ultrasound transducer 12, which converts these pulses into ultrasound transmit pulses. The electronic device receives electrical reception signals corresponding to the ultrasound echo pulses from the ultrasound transducer 12 . Furthermore, the front electronic device 14
receives the output signal of the temperature sensor 13.

The preelectronic device 14 is connected via a connecting line 15 to an evaluation device 16 which is arranged at an evaluation point A, which is remote from the measuring point M. The evaluation device 16 first has a signal processing circuit 17 . A running time measuring device 18 is connected downstream to this circuit. The signal processing circuit processes the signals transmitted via the connection line 15 from the front-end electronics 14 in accordance with the evaluation to be carried out. The running time measuring device 18 is
From the signal processed by the signal processing circuit 17,
The transit time of the ultrasonic pulse in the container 10 is determined, and the measuring device sends out a signal on the output side that can be used to indicate the filling state in the container 10 or to initiate a switching process depending on this filling state. do.

FIG. 2 shows, in the left part, a block diagram of the preelectronic device 14 at the measuring point M, and in the right part, the block diagram of the evaluation device 16 at the evaluation point A and the connecting line 15 between them. ing. The connecting line is shown as a dashed line because it can take any length. Second
The figure also shows an ultrasound transducer 12 and a temperature detector 13.

The front-end electronics 14 includes a control unit 2 which controls the time course of all processes in the front-end electronics.
has 0. In particular, the control unit 20 is connected to the output side 20.
Pulse generator 2 sends periodic trigger pulses to a
Send for 1. The output side of this pulse generator is connected to an ultrasound transducer 12. The transmission pulse generator 21 sends out high frequency transmission pulses based on each trigger pulse. This pulse has the desired optimal ultrasonic frequency and the ultrasonic transducer 1
2 into an ultrasonic transmission pulse. The duration of each transmit pulse is shorter than the transmit period. The transmission period is longer than the maximum transit time of the ultrasonic pulses in the container 10, ie the transit time of the container when it is empty or when it is at its lowest full state. As will be explained in more detail below with reference to FIG. 4, in the illustrated embodiment an ultrasonic pulse is generated which reaches the surface of the filling 17 from the ultrasonic transducer 12 in the container 10 and returns to the ultrasonic transducer 12 again. Assume that the maximum transit time is less than 250 ms and that the transmission period has a duration T _P of 500 ms and the duration T _S of each transmitted pulse is 1 ms. The control unit 20 therefore sends trigger pulses in each case at periodic time intervals of 500 ms to the transmission pulse generator 21, which on this basis sends high-frequency transmission pulses of 1 ms duration to the ultrasound transducer 12. Apply.

The trigger pulses periodically emitted at the output 20a of the control unit 20 are also fed to a blocking time interval circuit 22. The blocking time interval circuit 22, formed in the simplest case by a monostable multivibrator, delivers a blocking signal from its output on the basis of the respective trigger signal. The duration of this blocking signal T _BL corresponds to the "blocking time interval", ie the time during which the ultrasound transducer 12 cannot receive valid echo pulses. This is, on the one hand, the time during which the transmitted pulses are emitted and, on the other hand, the oscillation decay time following each transmitted pulse, ie the time during which the ultrasound transducer oscillates at a reduced amplitude. A similar electrical signal is generated at the connection terminal of the ultrasonic transducer 12 due to the reduced amplitude vibration, and the echo pulse that arrives during the vibration period is a signal whose amplitude of the electrical reception signal derived from this echo pulse is gradually attenuated. When it is smaller than the amplitude, it cannot be evaluated. The blocking time interval can vary widely depending on the characteristics of the ultrasound transducer, the ambient conditions (temperature) and the installation conditions. The duration of the blocking signal emitted by the blocking time interval circuit 22 is therefore set in such a way that it exceeds the maximum vibration damping time that occurs by a temporally safe factor. In the numerical example taken above, the blocking time interval T _BL is, for example, 6 ms from the start of the transmitted pulse.
It is.

The ultrasound transducer 12 is connected to the input 24a of an amplifier 24, which amplifies the electrical reception signal that the ultrasound transducer 12 sends out each time it receives an ultrasound echo pulse. The amplification degree of the amplifier 24 can be controlled by a voltage applied to the amplification control input 24b. Furthermore, the amplifier 24 has a blocking input 24c which is connected to the output of the blocking time interval circuit 22, so that the amplifier is blocked for the duration of the respective blocking signal delivered by the blocking time interval circuit 22. ing. The amplifier 24 is thus generated by the high-frequency transmission pulses emitted by the transmission pulse generator 21 as well as by the vibration damping of the ultrasound transducer 12.
oscillations are not transmitted and only the echo signal that arrives after the expiration of the blocking time interval appears at the output of amplifier 24.

In each transmission period in the filling state measurement, only valid received signals are generated which are derived from the ultrasound echo pulses reflected at the surface of the filling 11. This received signal is transmitted to the transmitting pulse generator 2
The high frequency pulse has the same carrier frequency as the high frequency transmission pulse sent out from the ultrasonic transducer 12, but its curve shape depends on the transmission characteristics of the ultrasonic transducer 12 and the container 1.
Since it is defined by the transmission state at 0, it differs from the curve shape of the transmitted pulse. Diagram A in FIG. 3 shows the transmission pulse generator 21 as an example.
Figure 2 shows a high-frequency transmit pulse emitted from a 100 MHz transmitter, assuming that the transmit pulses are keyed into a rectangular shape. Diagram B of FIG. 3 shows the received signal at the output of the amplifier 24, which corresponds to the received ultrasound echo pulse. The time interval T _M between the transmitted and received pulses is equal to the vessel 10
This corresponds to the transit time of the ultrasound waves at , which in turn represents the filling state. The amplitude and time course of the echo signal reproduce the transmission conditions in the container.

An envelope generating circuit 25 is connected to the output side of the amplifier 24, which generates an output signal corresponding to the time course of the envelope of the output signal of the amplifier 24. Diagram C in FIG. 3 shows the envelope signal extracted at the output side of the envelope generation circuit 25 for the received signal of diagram B. This envelope signal is
This is a voltage pulse with a time course corresponding to the envelope of the high-frequency signal of diagram B. This voltage pulse therefore contains all the information necessary for evaluation and determination of the transmission state. The envelope generating circuit 25 can be formed in the simplest case by an amplitude demodulator, optionally upstream of a bandpass filter tuned to the carrier frequency of the received signal.

The output side of the envelope generating circuit 25 is connected to the signal input side 26a of the logic switch circuit 26. A connecting line 15 is connected to the output side of this circuit. This logic switch circuit 26 has a control input side 27.
a, the input side of which is the second
It is connected to the output side 20b. A further control input 27b of the logic switch circuit 26 receives the blocking signal from the output of the blocking time interval circuit 22.

The output signal of the temperature detector 13 is applied to a further signal input 26b of the amplified logic switch circuit 26 in the amplifier 30.

The amplification control input side 24b of the amplifier 24 is connected to the output side of the amplification control circuit 60. This circuit delivers an amplification control voltage that affects the amplitude of an envelope signal corresponding to the received signal, as will be explained later.

However, due to amplification control, the information contained in the amplitude of the echo signal is lost through echo attenuation that damages the ultrasound pulse on its way from the ultrasound transducer to the filling surface and back to the ultrasound transducer. do. Since this information may also be important for the evaluation of the echo signal in the evaluation device, separate information regarding the echo amplitude is additionally transmitted to the evaluation device. For this purpose, an amplification control voltage delivered by an amplification control circuit 60 is applied to the input 29a of the voltage/time converter 29. The output of this converter is connected to a further control input 27c of the logic switch circuit 26. Voltage/time converter 29
A further input 29b of the control unit 20 is connected to an output 20b of the control unit 20. Voltage/time converter 29
outputs an output signal depending on the signal applied to the input side 29b. the duration of this output signal
T _V is dependent on the amplification adjustment voltage applied to input 29a.

The logic switch circuit 26 is connected to the control unit 20,
Blocking time interval circuit 22 and voltage/time converter 2
This is an electronic switching device that sequentially connects different signal lines 25 and 30 to a current driver 40 connected to its output side under the control of a time control signal supplied from 9.

Current driver 40 converts the respective signal voltage supplied by the logic switch circuit into a current which is transmitted via connection line 15 to evaluation device 16 . The connecting line 15 is therefore not driven as a voltage transmission line, but as a current loop.

A detector circuit 50 is connected to the current driver 40, which has a control input connected to a further output 20c of the control unit 20. The output side of the detector circuit 50 is connected to the input side of the amplification control circuit 60.

The evaluation device 16 has a microcomputer 70 which is programmed to carry out the functions of the signal processing circuit 17 and the running time measurement device 18 of FIG. Connection line 1 in evaluation device 16
A resistor 71 connected between 5 and ground closes the current loop. This voltage drop across the resistor 71 is added to the input side of the AD converter 72, and the digital output signal is sent to the microcomputer 70.
supplied to

The output side of the microcomputer 70 controls a switch 73 by means of which a voltage of +24 V can be applied to the connecting line 15. This voltage is significantly higher than the positive supply voltage V _CC used in front-end electronics, which is, for example, +12V.

The diagram in Figure 4 has a duration T _P = 500ms.
2 shows the signals transmitted via the connection line 15 during the course of a transmission period as a function of time. The durations of the various signals are not drawn to scale for clarity.

According to the numerical example given above, the duration of the transmission period T _P is selected to be more than twice the longest running time during which an echo pulse occurs. The transmission period consists of two equally large time segments T _P1 with a duration of 250ms.
and T _P2 . The division time T _P1 is
It is used for the transmission of the envelope signal corresponding to the echo pulse, while the remaining signals required for the evaluation of the envelope signal in the evaluation device 16 are transmitted in the segment time T _P2 . Of course, it is not necessarily necessary that the two time periods T _P1 and T _P2 have the same magnitude. For example, the segment time T _P2 provided for the transmission of the remaining signal is the segment time used for receiving and transmitting the echo signal.
It can also be made shorter than T _P1 .

At the time t ₀ at the beginning of each transmission period, the control unit 20 activates the logic switch circuit 2 synchronously with the trigger pulse emitted from the output 20a.
A signal is applied to the control input 27a of 6. This signal places logic switch circuit 26 in a position where a constant DC current I _A of, for example, 10 mA is applied to line 15. The start of this current pulse signals the evaluation device 16 when to send out the ultrasonic transmit pulse and thus the start of the measuring time. The duration of the transmission of the direct current I _A is preferably equal to the duration of the transmitted pulse T _S , which in the numerical example given here is 1 ms.
This duration is illustrated to be exaggerated in FIG. 4 compared to the duration T _P of the transmission period.

After the transmission time T _S has elapsed, the logic switch circuit 26 determines that the direct current applied to _the connecting line 15 is e.g.
It moves to a position where it is lowered to a relatively low value I _B of 6 mA. This state is maintained for the duration of the blocking time _TBL determined by the blocking time interval circuit 22. This blocking time is 6 ms from the beginning of the transmitted pulse in the numerical example described above. This indicates to the evaluation device 16 the duration of the blocking time. The blocking time T _BL is also shown in an exaggerated manner in FIG.

After the end of the blocking time _TBL at time _t2 , the logic switch circuit 26 switches the current driver 40 to the signal input 2.
Connect to 6a. Therefore, in the remainder of the first period T _P1 of the transmission period following the blocking time, the envelope signal I _H corresponding to the echo pulse is present in the evaluation device 1.
6. The evaluation device 16 determines at the transmission time t ₀
detecting a time interval T _M between and a time t _M at which the leading edge of the envelope signal I _H reaches a predetermined threshold;
The filling state in the container 10 is then calculated using the remaining signals and taking into account the transmitted parameters.

After 250 ms, the control unit 20 switches the control input 2 of the logic switch circuit 26 again at time _t3 .
At 7a, a signal is applied which serves to send out a synchronization pulse I _C of 1 ms duration with a current value of 10 mA. This synchronization pulse I _C indicates to the evaluation device 16 the start of the second segment time T _P2 of the transmission period.

However, since a trigger pulse is not generated at the output side 20a of the control unit 20 in conjunction with this synchronization pulse I _C , no ultrasonic transmission pulse is sent out at this point, and the blocking time interval circuit 22 is connected to the control input side 27b. No blocking signal is applied. The current in the connecting line 15 therefore drops to OV at the end of the synchronization pulse I _C at time t ₄ .
Since no current step of 6 mA occurs here, the evaluation unit 16 is able to distinguish between the two time periods T _P1 and T _P2 of the transmission period.

Duration determined by the output signal of the voltage/time converter 29 applied to the control input 27c
After the passage of T _V , the logic switch circuit 26 forms a connection between the signal input 26b and the current driver 40 from the time _t5 , so that the output voltage of the amplifier 30 changes to the corresponding direct current I _T in the connecting line 15. transmitted via. The connecting line 15 therefore carries a current I _T which is representative of the temperature in the container detected by the temperature sensor 13 during the remainder of the interval time T _P2 .
This current is maintained until the time t ₀ ' when the next transmission cycle begins and a new synchronization pulse with a current value of 10 mA is transmitted via the connection line 15.

The duration T _V determined by the voltage/time converter 29 depends on the amplification control voltage at the output of the amplification control circuit 60 and is therefore a measure for the echo amplitude. The voltage step change time t ₅ between the value OA and the temperature current I _T is therefore shifted depending on the echo amplitude. That is, in the segment time T _P2 , echo amplitude information is transmitted by the time signal and temperature information is transmitted by the current value.

In this way, all the information required at the evaluation point is transmitted via connection line 15 by means of very low-frequency signals. The connecting line 15 can therefore be a simple, unscreened conductor, and the transmitted signal is not significantly attenuated even if the length of the connecting line is very long.

Of course, different information can also be transmitted in different temporal sequences via the connection line, or the transmission format can be varied arbitrarily, in which case, for example, the echo amplitude can be represented by a current value. And the temperature is represented by time information. Further classification time
Further information of interest can be transmitted in T _P2 to the evaluation device using a similar low frequency signal.

In order to transmit the +24 V voltage pulse U _S by closing the switch 73 in _the evaluation device 16, the time _{window T} A time window T _F is provided, which is set such that the event does not occur within the same period. In Figure 4, the maximum period _TV is
It is assumed that it is less than 140ms. time window
T _F begins at time t ₆ 140 ms after the end of synchronization pulse I _C and has a duration of 60 ms, and thus ends at time t ₇ with a time interval of 200 ms from the end of synchronization pulse I _C.

The presence or absence of a voltage pulse U _S during the time window T _F indicates control information transmitted from the evaluation device 16 to the frontend electronics. By closing the switch 73, the connection line 15
When a voltage pulse U _S is applied to , it means "increase the amplification". Voltage pulse during time window T _F period
If _US does not occur, it means "reduce the amplification". Detector circuit 50 in front electronics 14
detects the presence or absence of the voltage pulse U _S in each time window T _F and controls the amplifier 2 by the amplification control circuit 60.
The amplification degree of 4 is changed accordingly.

An embodiment of current driver 40, detector circuit 50 and amplification control circuit 60 is illustrated in relative detail in FIG.

Current driver 40 has an amplifier 41 that acts as a voltage/current converter. A connection line 15 is connected to the output side of the amplifier via a resistor 42. Since the current I transmitted from the amplifier 41 via the connecting line 15 is always positive (FIG. 4), this current is connected to the output of the amplifier 41 at the resistor 42. A voltage drop is created such that the terminals of resistor 42 always conduct a relatively high potential. Amplifier 41 is configured to saturate at a positive supply voltage V _CC of +12V. Therefore, by closing the switch 73 in the evaluation device 16, +12V
When a higher voltage is applied to connection line 15, amplifier 41 can no longer deliver current and the polarity at resistor 42 is reversed. This polarity reversal is detected by detector circuit 50.

The detector circuit 50 includes a comparator 51 formed by an operational amplifier with a differential input. The inverting input side of the operational amplifier has two resistors 52,
It is connected to the tap of a voltage divider formed from 53. This voltage divider is connected between the terminals of a resistor 42, which is connected to an amplifier 41, and ground. The non-inverting input side of the operational amplifier is connected to connection line 1.
5, which is connected to the tap of a voltage divider formed by two resistors 54, 55, which are connected between the terminals of resistor 42 and ground.
The output of the operational amplifier carries a negative voltage when the potential applied to the inverting input is higher than the potential applied to the non-inverting input. That is, when the potential state is reversed, the output voltage of the operational amplifier becomes positive.

The output signal of comparator 51 is sent to holding element 57 via gate circuit 56 . Gate circuit 56
is controlled by a time control circuit formed from two monostable multivibrators 58 and 59 connected in cascade. The two monostable multivibrators 58 and 59 are triggered by the negative going pulse edge. The holding time of the monostable multivibrator 58 is 140 ms, and the holding time of the monostable multivibrator 59 is 60 ms.

The trigger input of the monostable multivibrator 58 is connected to the output 20c of the control unit 20. At each transmission cycle, the control unit 20 sends out a pulse to the output 20c that coincides in time with the synchronizing pulse I _C (FIG. 4). Monostable multivibrator 58 is triggered by the trailing edge of this pulse. After a holding time of 140ms, monostable multivibrator 58 becomes monostable multivibrator 5.
Trigger 9. Monostable multivibrator 59
is connected to the control input of the gate circuit 56, so that the gate circuit 56 is open for the duration of the holding time of the monostable multivibrator 59. As can be easily seen from FIG. 4, the opening time of the gate circuit 56 is exactly within the time window.
Corresponds to T _F. The output voltage of the comparator 51, which occurs during the time window T _F in each transmission period, is thus transmitted to the holding element 57. This voltage is stored in the timekeeping element until the beginning of the time window in the next transmission period.

Amplification control circuit 60 includes an integrator 61 formed by an operational amplifier 62 as in the prior art. A capacitor 63 is provided in a feedback circuit extending from the output side of this amplifier to the inverting input side.
The inverting input is connected via a resistor 64 to the output of the holding element 57 of the detector circuit 50, while the non-inverting input is connected to a fixed potential, for example ground potential. Corresponding to the known operation of this type of integrator, the output voltage of the operational amplifier 62 increases linearly when a constant negative voltage is applied to the input;
And when a constant positive voltage is applied to the input side, it decreases linearly. An inverting amplifier 65 is added to the integrator 61.
is postfix connected. The output of this amplifier delivers an amplification control voltage to an amplifier 24 and a voltage/time converter 29.

As is clear from the above explanation, the amplification degree of the amplifier 24 is such that the voltage pulse U _S
During and after each time window in which the voltage pulse U S is applied, it is increased continuously, while during and after the time window in which the voltage pulse U _S is not occurring, it is continuously reduced. The amplification degree of the amplifier 24 can thereby be controlled by the evaluation device 16.

Instead of the amplification degree of the amplifier 24, the voltage pulse U _S
It is also possible to control other functions of the front-end electronics. In a corresponding manner, a plurality of temporally successive time windows are set in each transmission period and one detector circuit is provided for each time window in the front electronics, which detects the voltage in the associated time window. Several functions of the front-end electronics can also be controlled by the evaluation device in such a way that it is detected whether a pulse has occurred or not. In each case, by applying significantly high voltages to the connection lines, it is ensured that the control signals transmitted from the evaluation device to the front-end electronics can be clearly distinguished from the envelope and information signals transmitted in the opposite direction. Guaranteed. By transmitting the control signal in the second segment time of each transmission cycle,
It is ensured that the transmission of the envelope signal in the partitioned time is not disturbed.

FIG. 6 illustrates a variant embodiment of the front-end electronics 14 in which the amplification of the amplifier 24 is not controlled by a control signal from the evaluation device. The block circuit diagram of the front-end electronics 14 roughly corresponds to the left-hand part of FIG. Circuit components that remain unchanged are provided with the same reference numerals as in FIG. 2 and will therefore not be described again. The front electronics of FIG. 6 differs from the front electronics of FIG. 2 only in the following respects. That is, instead of the amplification control circuit 60, an amplification adjuster 28 is provided. The amplifier regulator receives the output signal of the envelope control circuit 25 and maintains at a predetermined constant value an envelope signal at the amplification control input 24b of the amplifier 24, which corresponds to the amplitude of the received signal. The amplification adjustment voltage is sent out. The output side of the amplification adjuster 28 is
It is connected to the input side 29a of the voltage/time converter 29 in the same way as the output side of the amplification control circuit 60 in FIG. transmitted to.

Furthermore, FIG. 6 shows that the connection line 15 can be connected directly to the output of the logic switch circuit 26, so that the current driver 40 of FIG. 2 is omitted.

In this case, the connecting line 15 is not driven as a current loop, but as a voltage transmission line, and instead of the current values I _A , I _B , I _H , I _C , _IT shown in FIG. 4, corresponding voltage values result. . The time course of the transmitted voltage matches the time course of the current diagram in FIG.

[Brief explanation of drawings]

FIG. 1 is a block diagram illustrating the principle of an apparatus constructed according to the present invention for measuring the filling state in a container using an ultrasonic sounding device, and FIG. 2 is a block diagram of the apparatus according to the present invention. 3 is a block circuit diagram of an embodiment of the front electronics and evaluation device; FIG.
The figure is a waveform diagram showing the time course of various signals generated in the device of Figure 2, and Figure 4 is a signal waveform diagram showing the temporal sequence of signals transmitted via the connection line in the transmission period. , FIG. 5 is a circuit diagram showing in detail the construction of some components of the front electronic device of FIG. 2, and FIG. 6 is a circuit diagram of another embodiment of the front electronic device of the device of FIG. FIG. 3 is a block circuit diagram. M...Measurement point, A...Evaluation point, 12...Ultrasonic transducer, 13...Temperature detector, 14...Pre-electronic device, 15...Connection line, 16...Evaluation device,
17... Signal processing circuit, 18... Running time measuring device, 20... Control unit, 21... Transmission pulse generator, 22... Blocking time interval circuit, 24, 30
...Amplifier, 25...Envelope generation circuit, 26...
Logic switch circuit, 28...Amplification adjuster, 29
...Voltage/time converter, 43...Current driver,
50...Detector circuit, 60...Amplification control circuit,
73...Switch, T _P ... Transmission cycle, T _P1 , T _P2
...segmented time, I _H ... envelope signal, I _C ... synchronization pulse, _US ... control signal, T _F ... time window.

Claims (1)

[Scope of Claims] 1. A signal transmission device between an ultrasonic sounding device disposed at a measurement location and an evaluation location distant from the measurement location, the device being disposed at the measurement location. , at least one ultrasound transducer for transmitting ultrasound pulses in successive transmission periods and converting the received echo pulses into electrical signals after reflection at the target; A front electronic device having an envelope generation circuit for generating an electrical envelope signal representative of the envelope, an evaluation device arranged at the evaluation location, and a connection for transmitting the envelope signal to the evaluation device. and in the evaluation device, the envelope signal is evaluated in order to determine the target distance from the travel time of the ultrasonic pulse, and the generation and transmission of the envelope signal I _H are It is carried out in the first segment time T _P1 of the transmission period T _P , and the duration of the first segment time is short but equal to the longest possible transit time of the ultrasonic pulse, and the duration of the first segment time T P1 of the transmission period _T At a segment time T _P2 , for the evaluation of the envelope signal I _H , a low-frequency electrical signal I _T is generated at the measuring point M, characterizing at least the temperature of the propagation medium of the ultrasonic pulse, on the connecting line 15. is transmitted to the evaluation point A via the transmission period T _P
At least one control signal U _S is transmitted from the evaluation point A to the measuring point M via the same connection line 15 in a second time period T _P2 of , and the control signal U _S is transmitted in each case during the same time period T P2. 1. A signal transmission device characterized in that the signal transmission device is formed so as to be distinguishable from a low frequency signal transmitted in the. 2 In the evaluation device 16, each transmission cycle
A device 73 is provided for applying at least one control signal U _S to the connecting line 15 during a predetermined time window T _F in a second time interval T _P2 of T _P , and Claim 1: A detector circuit 50 is provided in the frontend electronic device 14, which is responsive to the occurrence of a control signal _US during a predetermined time window T _F in each transmission period T _P. Signal transmission device as described in section. 3 In order to increase the respective control signal U _S , a voltage higher than any voltage occurring on the connecting line 15 during the transmission of the low-frequency electrical signal is detected during a predetermined time window.
The signal transmission device according to claim 1 or 2, wherein the signal is applied to the connection line during the period of _TF . 4. Any one of claims 1 to 3, in which an electrical signal characterizing the amplitude of the received echo pulse is transmitted to the evaluation point A at the second segment time T _P2 of each transmission period T _P The signal transmission device according to item 1. 5. Any one of claims 1 to 4, wherein at least one of the electrical signals transmitted during the second segment time T _P2 of each transmission period T _P is indicated by amplitude information. The signal transmission device according to item 1. 6. The signal transmission device according to claim 5, wherein the amplitude information is represented by a direct current _IT . 7 Second division time T _P2 of each transmission period T _P
7. The signal transmission device according to claim 1, wherein at least one of the signals transmitted during the period is displayed by time information _TV . 8. The signal transmission device according to claim 7, wherein the time information _TV is displayed by the time point of switching from one amplitude value to another amplitude value. 9 Envelope generation circuit 2 in front electronic device 14
An amplifier 24 is pre-connected to 5, the amplification of which varies depending on the amplification control voltage, and a signal is provided to the preelectronic device 14 for generating a low frequency signal dependent on the amplification control voltage. A source 29 is provided, and the low frequency signal has a respective transmission period.
The signal transmission device according to any one of claims 1 to 8, wherein the signal transmission device is transmitted to the evaluation point A at the second segment time T _P2 of T _P. 10. The signal transmission device according to claim 9, wherein the signal source is a voltage/time converter 29 that generates a time signal dependent on the amplification control voltage. 11 The amplification control voltage is determined by each transmission period T _P
11. The signal transmission device according to claim 9 or 10, wherein the signal transmission device is determined by a control signal transmitted from the evaluation point A to the measurement point M during the second segment time T _P2 . 12 The amplification control voltage is an amplification control circuit 6 that controls the level of the envelope signal I _H to a predetermined value.
11. The signal transmission device according to claim 9 or 10, wherein the output voltage is zero. 13 Each division time T _P1 of the transmission period T _P ,
At the start of T _P2 , the electrical signal I _A , characterizing this start,
13. The signal transmission device according to claim 1, wherein I _C is transmitted to evaluation point A via the same connection line. 14 The frontend electronics 14 includes a control unit 20 for controlling the transmission of the ultrasound pulses and the time sequence of the signal transmission from the measurement location M to the evaluation location A, and that the control unit 20 controls the generation of the ultrasound pulses. A first synchronization pulse I _A at the start of the first segment time T _P1 of each transmission period T _P
of the second synchronization pulse I C via the connection line 15 and triggering the transmission of the second synchronization pulse I _C via the connection line 15 at the beginning of the second segment time T _P2 of the respective transmission period T _P . The signal transmission device according to item 13. 15 The front electronic device 14 is a logic switch circuit 26
The signal input side of the logic switch circuit is connected to the output side of the envelope generation circuit 25 and the output side of another signal source 13, 29 that generates a low frequency electric signal, and the logic switch circuit includes The output side of is connected to the connection line 15, and the logic switch circuit is controlled by the control unit 20 to control the connection line 15 for the first segment time T _P1 of the respective transmission period T _P.
Claim 14, wherein the signal generator is connected to the output side of the envelope generating circuit at the time of transmission and is controlled to be connected to at least one further signal source at the second segment time T _P2 of each transmission period T _P . Signal transmission equipment.