SU370548A1 - METHOD OF MEASURING DYNAMIC RESISTANCE OF ELECTRIC CONTACTS - Google Patents

Description

one

The invention relates to radio electronics, telemechanics and communications, and can be used to test, study and control the reliability of periodically switched off electrical contacts, for example, relays, remote switches, coordinate connecting and similar devices.

According to a known method of measuring dynamic resistance of the first kind of closed contacts, which occurs when external vibrations are applied to the contacts, the voltage from the contacts and the reference resistance are alternately applied to the input of the oscilloscope. The contacts are supplied with stabilized voltage, the specified contact load current is set, the shunt resistance of the multichannel gauge measuring device is simultaneously switched into the reference resistance circuit and the current through this resistance, gradually changing the current magnitude, aligning the flat top of the calibration pulse on the oscilloscope screen on the reference resistance, with the test portion of the voltage variation curve at the contacts, and measure the value of the measured resistivity effects on the instrument scale, which is determined depending on the previously performed switching of load currents, shunts, and measurement limit, synchronizing alternately the supply of voltages to the oscilloscope input and the voltage of its waiting sweep with a frequency multiple of the vibration frequency. However, the known method of measurement cannot

apply when measuring the dynamic resistance of the second kind, which is formed with each closure of the contacts of the LOD by the influence of the vibration of the contact springs that occur spontaneously (in the majority of

cases) with mechanical connection of contacts, as well as due to mechanical, electrical and thermal processes observed at the time of contact closure.

According to the proposed method, in order to simplify the process of measuring the dynamic resistance of electrical contacts, a calibration mark is formed at the end of the measurement cycle, gives it a L-shaped shape and, by adjusting

the current in the reference resistance circuit, move the horizontal part of the label to the level of the investigated section of the voltage change curve on the measured contacts, read the dynamic resistance value, for example, with a digital device, and then move the vertical part of the label to the same section of the curve, while adjusting the duration of the switching-on relay switching relative to any moment in

during the operation of the investigated relay, and count the duration of the specified delay, for example, a digital intervalometer.

FIG. Figure 1 shows a variant of a block diagram of a device for measuring dynamic resistance of the second kind with the method proposed; in fig. 2 - waveform, obtained in the measurement process.

The contacts 1 of the relay 2 under study are fed from the source through the resistance 3 of the load. A 4-pulse generator is connected to the relay 2 winding. The generator is powered by pulses with a start-up pulse 5 and a counter 6, and the measuring switch 7 supplies the locking pulses. The switching relay 8, the counter 6 (stop), the key 7 (off) and the waiting multivibrator 9 feed the delayed pulses through the delay node. key 7.

The input of the oscilloscope 10 is connected to the output of the measuring key. An external triggering of the synchronization is carried out by the sensor 11 clock pulses, which also gives a starting impulse to the waiting multivibrator 12 with an adjustable delay time. Multivibrator includes key 7.

A digital voltmeter 13 is connected to a calibration resistance 14, the voltage at which is regulated by a variable resistance 15.

After switching on the circuit, relay 2 periodically closes the contacts / and each time the normally closed contacts are opened, the sensor 11 of the clock pulses the waiting scan of the oscilloscope and an image of the process being studied appears on its screen (see Fig. 2). The following waveform is taken on the oscillogram shown:

a - opening of closed contacts (the beginning of the flight);

b - the first touch of open contacts; (interval b-a (duration of flight);

e - the end of the bounce interval; b - the duration of the bounce; point in relation to the start of the process (winding on) determines the response time

g - the first activation of the measuring key;

d - off the measuring key;

e-activation of the switching relay;

g - the second switching on of the measuring key;

gd - calibrated length of time;

3 - the second shutdown of the measuring key (the end of the process under study);

d-W - vertical moving calibration time stamp;

k - horizontal moving calibration mark of resistance.

Adjusting the delay of the multivibrator 12 shifts the point g relative to the point b, changing the moment of switching on the measuring switch

, 370548

and thereby protecting the measuring system from overloading.

The vertical calibration time stamp is moved by adjusting the delay in the delay node 5. Since the digital counter of clock pulses (intervalometer) for starting and stopping, receives a pulse from the generator 4 and the delay node 5, the indicator reads the time from the process start to the required time, for example, until the resistance stabilizes as in FIG. 2. The horizontal calibration mark of the resistance is moved by changing the voltage on the resistance 14 and adjusting the resistance 15 included in the voltage divider (not shown). A digital voltmeter indicator is measured in units of resistance, for which the indicator is moved one digit to the right each time the load current decreases by a factor of 10. For example, use a W-1512 voltmeter in the range O-1,099996, with

load current 1 and the counting is in ohms, at a current of 0.1 and the first discharge means ten ohms, etc.

With the aid of a calibrated d-g interval, parameters of the dynamic resistance, for example, the frequency of the variable component of the resistance, are additionally measured.

Subject invention

A method for measuring the dynamic resistance of electrical contacts, based on the registration by an electronic oscilloscope of alternately replaceable images of the process of changing the resistance of contacts after their

The moving and image of the moving calibration mark, which is formed by switching the switching relay of the oscilloscope input from the contacts under study, energizes a sample current, characterized in that, in order to simplify the measurement process, the calibration mark is formed at the end of the measurement cycle. By adjusting the current in the reference resistance circuit, the horizontal part of the mark is moved to the level of the investigated section of the voltage change curve on the measured contacts, d t read the dynamic resistance value, for example, with a digital device, and then move the vertical part of the label to the same part of the curve, while adjusting the delay time for switching the switching relay relative to any moment during operation of the relay being investigated, and counting the duration of the specified delay, for example digital intervalometer.