SU1530926A1 - Acoustic level gauge - Google Patents

Abstract

The invention relates to a measurement technique, namely, means for measuring distances to the interface between two media by an acoustic method. The method makes it possible to increase the measurement accuracy by fixing the arrival time of the reflected probe pulse as it passes through zero, i.e. on the signal section with its maximum steepness, and the independence of the response time from the signal amplitude. For this, the second comparator 18 is triggered into the auto-circulating measuring channel of the level gauge, triggered by a signal passing through the zero level and gated by a delayed signal from the output of the first comparator 12. The device contains an auto-circulating measuring channel 1 connected to the counting input of the trigger 2 of the counter gate. The time interval between the signals from the output of this counter (the period of auto-circulation) is filled with high-frequency pulses coming from the output of the frequency sensor 7 temperature to the counting input of the counter. The source of the reference voltage 14 of the first comparator 12 is made in the form of a voltage divider. 2 Il.

Description

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The invention relates to the measurement of acoustic methods and can be used in the control and measurement of the level of liquid media, for example, in wells and canals of reclamation systems.

The purpose of the invention is to improve the interference tolerance.

Figure 1 shows the structural diagram of the acoustic level gauge; figure 2 - the timing diagram of the work.

The level gauge contains an autoirculation measurement channel 1 connected to the trigger input 2 of the gate formation, outputs 3.1 and 3.2 of which are connected to the first inputs 4.1 and A.2 of the counter 5, the second pass 6 of which is connected to the output of the frequency sensor 7 of the temperature.

The autocirculation measuring channel 1 is implemented as an emitter 8 and P1ka 9 receives acoustic oscillations installed in the measuring tube 10 and BKjno4eHHix in the auto-circuiting circuit with amplifier 11, the first comparator 12 connected by a second input to the output 13 of the source 14 of the reference voltage one-shot 15 and block 16 excitation probing them

pulses, the autocirculation circuit also includes a delay unit 17 and a second gated comparator 18, the first input of which is connected to the first bus 19.1 of the power supply and the first input of the source 14 of the reference voltage,

the second input is with the output of amplifier 11 and the first input of the first comparator 12, the third gate input with the output of the connected input with the output of the first comparator 12 of the delay block 17, and the output with the input of the one-oscillator 15, the output of which is also connected to the input of the strobe formation trigger 2, wherein the second power supply bus 19.2 is connected to the second input of the source 14 of the reference voltage.

The source 14 of the reference voltage is in the form of a voltage drop across the resistors 20 and 21, the middle point 22 of the voltage divider is the output, one output is the first input, and the other is the second input of the reference voltage source.

When the power is turned on, block 16, executed, for example, in the form of auto-generator synchronization (KOT ip T synchronous input (i is the input of the

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16, and the output is the output of the block 16), and using a radiator 8, the probing acoustic pulse in the measuring tube 10, which, having reflected from the surface of the liquid, reaches the input of the receiver 9 and is perceived by it. The latter transforms the acoustic impulse into 3J; is acoustic, while the amplifier 11 amplifies it.

The amplified innuli 2 (Fig. 2) is fed to the first input of the first comparator 12 and when the level 24 of the source 14 of the reference voltage is reached causes the first comparator 1 2 to operate.

Thus, interference is eliminated by the amplitude feature: if the incoming pulse 23 is less in amplitude than level 24 of source 14 of the reference voltage (i.e., less than amplitude of useful signal, since level 24 is chosen equal to the minimum level of useful signal), the first comparator 12 does not work and the signal further to the autodirculation channel 1 does not pass.

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MPL 25 (Fig. 2) from the output of the first comparator 12 y:; i.e. bg, about 17 zader / Kp, filled, for example, in the form o and ::,} of the zibrator, for a time T (fit- .2, by them 26). This pulse is gating for the second comparator 18; therefore, when the signal reaches level 23, it triggers (since its first input is connected to the first power supply bus 19.1, which is a common bus) and forms a square pulse 27, which charges the single vibrator 15 .

Thus, the second comparator 18 is triggered at the moment of the greatest slope of the signal at its input, which ensures the highest accuracy of its response over time, and consequently, the highest accuracy of the entire autocirculation measuring channel 1, since the result of the measurement is determined by the signal arrival time.

On the leading edge of the output pulse 28, the one-shot 15 is synchronized by the generator 16, excited again by the emitter 8, the probing acoustic pulse in the measuring tube 10, i.e. the process repeats and the probe pulse auto-circulate occurs.

The output signal 28 of the single-conductor 15 is also fed to the counting input of the strobe formation trigger 2, which produces start-stop signals 29.1 and 29.2 for counter 5. The time interval between the Start 29.1 signals from output 3.1 and Stop 29.2 from output 3.2 is filled with high-frequency pulses (not ) coming from the output of the frequency sensor 7 temperature to the input 6 of the counter 5. This allows the counter 5 to register the duration of the anthocirculation period of the probe pulse corresponding to the distance to the liquid level with simultaneous compensation temperature error setting.

The duration T, the delay of the output signal of the first comparator 12 is chosen from the condition

t t „+ t + t, b.

where T is the lag time of the decay to zero of the first half-wave of the signal 23 with respect to the trailing edge of the output pulse 25 of the first comparator 12, s; T - second response time

comparator 18, s;

  response time of one-shot 15, sec.

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Claims (1)

Claims of the invention Acoustic level gauge, containing a strobe trigger, the outputs of which are connected to the first and second inputs of the counter, a frequency temperature sensor and an auto-circular pion measuring channel containing a series-connected one-oscillator, an excitation unit and an emitter, as well as a receiver of acoustic oscillations coupled to an amplifier, characterized in that, in order to increase the noise immunity, the circulation channel is additionally equipped with first and second gating comparators, a block Support and source of reference voltage, while the output of the amplifier is connected to the first input of the first comparator and the first input of the second gating comparator, the output of which is connected to the input of the one-vibrator, the second input of the first comparator is connected to the first bus of the source of reference voltages, the second bus of which is connected to the second the input of the gating comparator, the output of the first comparator is connected to the input of the gating of its second building comparator, and the output of the frequency temperature sensor is connected to the third input counter house. five 0 five 26 J. / 29T 12  29.2 ai .. FIG. g