SU600434A1 - Gaseous medium thermal-physical parameter monitoring device - Google Patents

Description

a capacitor, a resistor, a direct current source with polarity, inverse to the polarity of the main source, an additional electronic key having conductivity, inverse to the conductivity of the main key, and connected between the common connection point of the resistor with the capacitor in the additional circuit, and by a periodic delay block connected between the synchronizer output and the control key of the additional switch.

The drawing shows a diagram of the proposed device.

The device contains a piezoelectric emitter 1 and a receiver 2 installed in a controlled environment, connected in parallel to the emitter is a series circuit consisting of a capacitor 3, a resistor 4 and a source 5 of direct current voltage, an inductance coil 6, an electronic switch

7 connected to the connection point of capacitor 3 and resistor 4 and to the common connection point of inductance coils 6, radiator 1 and voltage source 5, synchronizer

8, the output of the key 7 connected to the control electrode 9, the time measurement unit 10, one of the outputs of which is connected to the output of the synchronizer 8 through the delay unit 11, the amplifier 12 connected between the receiver 2 and the second input, the time of the measuring unit 10, and the registering unit 13 connected to the output time of the measuring unit 10.

The device also includes an additional circuit connected in parallel with the emitter 1, consisting of a capacitor 14, a resistor 15 and a source 16 of a DC voltage having a polarity opposite to that of the main source 5, an additional electronic switch 17 having a conductivity, inverse conductivity the main switch 7, and connected between the common point and the connection point of the resistor 15 with the capacitor 14 in the additional circuit, and the half-period delay unit 18 connected between the output of the synchronizer 8 and the control electrode 19 additional key 17.

A contour acoustic emitter consisting of a piezoelectric element and a shunt inductance coil 6 of it, using keys 7 and 17, are used to excite electric shock effects. The first of these shocks on the emitter 1 is the electronic negative voltage across the switch 7 controlled by the synchronizer signals 8. In the absence of signals, the capacitor 3 is charged through the charging resistor to the voltage E of the source 5 voltage. With the pulse signal of the synchronizer 8 being fused to the electrode 9, the switch 7 opens and the capacitor 3 discharges through switch 7, affecting the emitter 1 with a voltage drop. Under the action of this differential, in the circuit formed by the static capacitance of the diezoelectric emitter 1 n inductance of the coil 6, damped electrical oscillations occur. In order for the frequency of these

electric oscillations coincided with the resonant frequency of the piezoelectric element, the inductance L of the coil 6 is set close to 0.025, where C is the static capacity of the piezoelectric element of the radiator 1.

After a period of time equal to 0.5 / ciezo-emitter 1, it is excited by a second differential voltage of positive polarity. This difference is created by the discharge of the capacitor 14, charged in a static state through a resistor 15 to the voltage Eg from the source 16 by means of a switch 17. The latter, using block 18, is turned on by a synchronizer pulse 8 after half a period of 0.5 resonant oscillations

piezoelectric element radiator. If the first differential electric voltage were not applied to the loop transducer, under the action of the second differential there would have been damped electrical oscillations, similar in shape to the vibrations caused by the first differential, and inverse to them.

Since these oscillations are shifted in time by half of their period, under the influence of both differential waves, the oscillations add up in phase relative to each other. At the same time, the resulting oscillations have an amplitude that is about twice as large as the amplitude of oscillations at a single excitement by any of these two differences. Along with an increase in amplitude, another effect is also achieved here. It consists in the fact that the pulse has a more symmetrical shape, which provides a higher monofrequency

excitation and information content of the emitted pulse, which improves the accuracy of measuring the propagation time of the emitted oscillations in a controlled environment. Periods of drops cyclically

with a period of following, usually much longer than the duration of the resulting high-frequency pulse of damped oscillations, exciting the piezo emitter. By the action of pulses, the piezoelectric element of the emitter 1 emits, in a controlled environment, pulses of ultrasonic vibrations with a frequency f, which propagate in it at a speed depending on the density of the gas and its temperature. At a constant flow rate, the propagation time of the ultrasound pulse from radiator 1 to receiver 2 is determined by the amount of heat carried by the gaseous stream in which the radiator and receiver are located.

The ultrasonic pulses received by receiver 2 are converted into electrical pulses with a carrier frequency equal to the frequency / ultrasonic vibrations. The converted pulses are amplified in the amplifier.

12 and one of the inputs of the time measuring unit 10, to another input of which is fed through the delay unit 11, pulses from the output of the synchronizer 8. The delay time here is set to the transit time corresponding to the initial value of the thermophysical parameter being monitored - the amount of heat.

Under the action of incoming pulses during the measuring unit 10, a rectangular electric pulse is formed, having a duration equal to the time interval between the arrival of a pulse from the amplifier 12 and from the AND block of the delay. A rectangular pulse is converted into an electrical voltage proportional to the duration of this pulse and, accordingly, to the parameter being monitored, which is fed to the recording unit.

Claims (2)

1.Briger G. And., Etc. Ultrasonic flowmeters. M., 1964, p. 305-312. 2. US patent L 2565725, cl. 73-67.5, 1968.