SU1567895A1 - Leakage detector - Google Patents

Abstract

The invention relates to the test of leaktightness using the probe method and allows for improved performance while maintaining sensitivity. The leak detector contains a series-connected probe 1, a sensing element 2, an ion current measurement unit 3 and a summing amplifier 4. A pressure measurement unit 6 is also connected to the probe 1 and a scale amplifier 7, the output of which is connected to the second input of the summing amplifier 4 and the input of the inverting comparator 9. The second input of the latter is connected to the engine of the variable resistor 11, one extreme end of which is grounded, and the other is connected to the generator 12 of the sawtooth voltage. The alarm unit 16 of the unsteady mode is connected to the switch 13 and the input of the comparator 9, the input of the switch 13 to the controllable input of the electrically controlled valve. The latter is made in the form of a housing 25 with a saddle 26. The locking member 27 is spring-loaded relative to the saddle and can move in the opposite direction under the action of the electromagnetic forces of the winding 14. When the leak detector is turned on, the pressure in the system is large, the block 16 issues a signal and the locking member 27 closes the saddle 26. After setting the allowable pressure, the valve opens smoothly. 1 hp ff, 2 ill.

Description

The invention relates to a control and measuring technique and can be nonsense 'hours; -sh <when tested n. ·; ι leakproof. using test gas using the blunt method, as well as automating the test process.

The aim of the invention is to improve performance while maintaining sensitivity.

In FIG. 1 shows a leak detector circuit; in FIG. 2 is a timing diagram of a leak detector.

The leak detector contains a serially connected probe 1 for sampling gas, a sensing element 2, an ion current measuring unit 3, a summing amplifier 4, and a leak indicator 5. The probe 1 is connected through a unit 6 of pressure, and a pressure amplifier and an amplifier 7 with an inverting input of the summing amplifier 4, with the first input of the recording unit 8 and with the inverting input of the comparator 9 of the unit 10 for automatically regulating the probe cross-section 1. Non-inverting the input of the comparator 9 is connected to the engine of the variable resistor 11 "Installing the cross section", one extreme terminal of which is connected to a common bus, the other extreme terminal is connected to the output of the sawtooth generator 12. The output of the comparator 9 through the operating mode switch 13 is connected to the electromagnetic coil 14 of the probe 1, with the D-input of the first D trigger 15 of the transient signaling unit 16, and with the C-input of the second D-trigger 17. The D-input of the latter is connected to the common bus and through a capacitor 18 it is connected to its S-input, while the non-inverting input of the D-flip-flop 17 is connected to the C-input of the D-flip-flop 15, the inverting output of which is connected to the input of the generator 20. The output of the latter is connected to the input of the amplifier 21 of the audible alarm, and through the resistor 22 and 23 soy LED Inonii to sheathe bus, the output of the amplifier 21 via the element 24 chime connected to a common power bus. The second output of the winding 14 of the probe 1 is connected to a common bus through the housing 25 of the probe 1. The latter has a cone-shaped seat 26 on one side. A cone-shaped cylindrical locking element 27 of ferromagnetic material is placed on it, spring-loaded by a spring 28 to the seat 26, and the other end of the spring 28 through a replaceable tip

29. having a maximum cross-sectional area permissible for a given accuracy class

30, threaded connection to the housing 25 of the probe I.

Leak detector works as follows.

When the leak detector is turned on, when the pressure in its vacuum system is high, high voltage levels appear at the output of the pressure measuring unit 6 and the output of the scale amplifier 7, the output level of the comparator 9 is low (Fig. 2b; dir. 1), to the probe winding 14 I no voltage is supplied, which completely blocks the bore 26 of the probe 1. D-flip-flop 17 at the non-inverting output generates (at the moment of switching on) one short pulse of negative polarity (Fig. 2c), by the positive edge of which it is set at the inverting output of the D-flip-flop 15 tsya level "1" (Fig. 2d) is included generator 20 (FIG. 2d), illuminates the LED 23, and through the amplifier 21 and the member 24 an audible alarm that indicates the presence of high pressure in the vacuum system (transient operation).

With further pumping of air, the pressure in the vacuum system of the leak detector decreases (Fig. 2a, dir. 2), this leads to a decrease in the voltage level at the output of the scale amplifier 7 and the appearance of a pulse-width-modulated '(PWM) signal at the output of the comparator 9 (Fig. 26), and the higher the pressure in the vacuum system, the lower the voltage level at the output of the amplifier 7 and the more “wide” pulses of a PWM signal of positive polarity at the output of the comparator 9 (Fig. 26), which leads to an increase in the average flowing through the winding 14 current and stole the increase in the magnetic flux generated by the winding 14, and this moves the shut-off element 27 to the tip 29, which increases the passage section 26 and the air flow from the atmosphere through the probe 1 into the leak detector vacuum system, which is an inertial integrating link for the error signal in the automatic control system of the passage section.

The PWM signal from the output of the comparator 9 is fed to the C-input of the D-flip-flop 17, at the non-inverting output of which there are pulses of negative polarity (Fig. 2c) with a duration proportional to the time constant of the RC chain (19 and 18). These pulses are fed to the C-input of the D-flip-flop 15, to the D-input of which pulses of the PWM signal come from the output of the comparator 9. The D-flip-flop 15 compares these pulses by duration. If the pulse width of the PWM signal is less than the pulse duration at the output of the D-trigger 17 (Fig. 2d, dir. 2) (transient mode), then by the positive edge (edge) of the pulses from the D-trigger 17, the D-trigger 15 is set to "0 ", A constant level <1" is set at its inverting output, the light and sound signaling is turned on (Fig. 2e), and the operator interrupts the control until the leak detector automatically returns to normal operation.

If the pulse width of the PWM signal is longer than the pulse duration at high 1567895 during D-flip-flop 17 (Fig. 2, dir. 2-3), according to the positive difference of which the D-flip-flop 15 is set to “1”, the level “O” appears on its inverting output "(Fig. 2d), the generator 20 turns off, the LED 23 goes out and the sound alarm element 24 turns off, which allows further monitoring.

The value of the required steady-state pressure in the leak detector vacuum system (the limits of automatic control of the bore) is set by the resistor 11 by changing the amplitude of the sawtooth voltage (Fig. 2, dir. 4), which changes the ratio between the pressure signal level and the pulse width of the PWM signal.

The recording unit 8 documents the presence of leaks in the controlled product and any changes in pressure in the vacuum system during the control.

The switch 13 of the operating mode during setup of the device connects the winding 14 of the probe to the positive bus of the power source, the flow area of the probe 1 is changed to the maximum value, the pressure in the vacuum system increases, and at its required value, the resistor 19 sets the response threshold of the transient signaling unit 16 by changing the duration of the reference pulses of negative polarity at the non-inverting output of D trigger 17. If the operator needs to accelerate the process of the leak detector reaching ANOVA mode, the switch 13 is set to "pumping Express", the winding 14 is disconnected from the probe 1, the automatic control system, through hole probe 1 completely overlaps the valve 27, which reduces the air flow from the atmosphere into the vacuum system. When the alarm unit 16 is turned off, the switch 13 is set by the operator to the “Operation” position.

The device can be implemented on series 140, K621, and K155 microcircuits, which reduces its dimensions, cost, and increases the reliability and manufacturability of the device.

Using a leak detector can significantly increase the performance and reliability of monitoring, reduce operator fatigue and makes it possible to automate the monitoring process, since the need for frequent manual adjustment of the probe cross-section and pressure in the leak detector vacuum system is eliminated, which often distracts the operator and requires his constant presence.

Claims (2)

Claim 1. A leak detector containing a gas probe connected in series, a sensing element, an ion current measuring unit, a summing amplifier and a leak indicator, a pressure measuring unit and a scale amplifier connected in series with the probe, the output of which is connected to the second input of the summing amplifier, source a reference voltage, an inverting comparator, the inverting input of which is connected to the output of the scale amplifier, and a recording unit connected to the output of the scale amplifier, characterized in that In order to improve operational characteristics while maintaining sensitivity, the reference voltage source is made in the form of a sawtooth voltage generator, the probe is made with an electrically controlled valve, and the leak detector is equipped with a variable resistor, a three-position switch and a transient signaling unit connected to the first output of the switch, the input of which is connected to a controlled input electrically controlled valve, the second · output is grounded, and the third is connected to the positive bus of the power supply, block cancellation of transient mode is made in the form of series-connected first and second D-t, jagers, pulse generator, sound alarm amplifier and connected in parallel with its last cathode via an LED resistor, the C-input of the first D-trigger is connected to the D-input of the second D- trigger, the D-input of the first D-trigger is grounded and connected to its S-input through a capacitor, the C-input of the first D-trigger and the D-input of the second D-trigger are combined and form the input of the transient signaling unit, connected to the output of a device, the non-invertible input of which is connected to the engine of a variable resistor, one input of which is grounded, the other is connected to a sawtooth generator, and the anode of the LED and the output of the audio signal amplifier through the sound signal element are grounded. 2. Leak detector for π. 1, characterized in that the electrically controlled valve is made in the form of a body with a cone-shaped seat, a locking member made of ferromagnetic material spring-loaded to the seat, and an electromagnetic coil mounted on the outer surface of the housing with the possibility of magnetic movement of the locking member away from the seat. U _with Mode 1 \ Mode2 \ Modeb \ Mode 4 a b g d FIG. 2 Reda ctor A. Dolinich Order 1316