RU2307367C1 - Auxiliary block for indicating contact of measuring device with the object being checked - Google Patents

Abstract

FIELD: measuring equipment.

SUBSTANCE: device contains generator of signals, different from signals, existing in object being checked, current-limiting unit and signal meter. Output of signal generator is connected to input of current-limiting unit. Input of signal meter and output of current-limiting unit are connected to object being checked in same point with measuring device.

EFFECT: simplification of device.

2 dwg

Description

The invention relates to the field of measurement technology and can be used in conjunction with measuring devices to indicate their contact with the object being checked.

A drawback of many existing measuring devices is the lack of information about the contact between the probes of the measuring device and the test object, which is of great importance when working with a logic probe or when measuring voltages that can take a zero value. Typically, this drawback is compensated by excessive force applied to at least one of the probes, which in turn can lead to mechanical damage to the tested object. However, there are technical solutions to determine the presence of contact during measurement. For example, in the device according to the copyright certificate No. 646279 “Device for monitoring the contacting of integrated circuits”, IPC G01R 31/28, application No. 2428043 dated 10.12.76, a specially generated signal is used to determine the presence of contact, which is fed through electronic keys to the integrated circuit being checked. The measurement unit, upon detection of this signal at its inputs, makes a decision about the presence of a contact.

During the operation of the above device, a certain test signal must be supplied to the tested object in advance, which is impossible to carry out in most cases of electrical and radio measurements.

According to the operating principle, the closest to the proposed technical solution is a logical probe presented in the copyright certificate No. 1045179 with priority dated January 28, 1982, IPC G01R 31/28, application No. 3388796.

The structural diagram of the above logical probe is shown in figure 1, where the following notation:

1 - pulse generator;

2 - resistor;

3 - limiter;

4 - element of comparison;

5 - integrating element;

6 - indication element.

The logic probe contains a pulse generator 1, a resistor 2, a limiter 3, a comparison element 4, an integrating element 5 and an indication element 6. The input of the logic probe is connected to the first input of the limiter 3 and through resistance 2 to the output of the pulse generator 1, also connected to the first input of the element comparison 4. The second input of the comparison element 4 is connected to the output of the limiter 3, and its output is connected to the input of the integrating element 5, the output of which is connected to the input of the indication element 6.

The operation of the logic probe is based on the fact that, in the absence of contact between the logic probe and the object being tested, the same signals arrive at the first and second inputs of comparison element 3, which are indistinguishable for it. There is no contact signal. Display element 6 is turned off.

When the logic probe is in contact with the test object at the first and second inputs of the comparison element 3, the signals become different, and the indication element 6 is turned on.

This device is schematically quite complex.

The technical result of the invention is the ability to indicate the contact of the measuring device with the tested object using a device simple in circuit design, i.e. simplification of the device.

The above technical result is achieved using a device containing a signal generator, a signal meter and a current-limiting unit. The current-limiting unit is connected by an input to the output of a signal generator other than the signals existing in the measurement object, and by an output - with a common connection point of the object being checked, the signal meter and the measuring device. Moreover, the level of limitation of the current-limiting unit is chosen so that the current through the current-limiting unit during measurements does not cause an unacceptable error in the measuring device.

The figure 2 shows a block diagram of the proposed device and the following notation:

1 - current-limiting node;

2 - a generator of signals other than signals existing in the tested object;

3 - signal meter.

The proposed device contains a signal generator 2, different from the signals existing in the tested object (hereinafter referred to as the signal generator), a current-limiting unit 1 and a signal meter 3. The output of the signal generator 2 is connected to the input of the current-limiting unit 1, the output of which is connected to a common connection point of the object being checked , signal meter and measuring device.

The device operates as follows. In the absence of contact with the tested object, the current does not flow through the current-limiting node 1, the signals at the input and output of the current-limiting node 1 will be the same, approximately the same as at the output of the signal generator 2. In this case, the signal meter 3 captures a signal equal to the signal of the generator 2.

In the presence of contact with the tested object through the current-limiting node 1, current will flow due to the presence of a signal from the tested object. In this case, the signal meter 3 will record a signal that does not match the signal of the generator 2.

One of the options for the possible implementation of the inventive device and its operation will be considered on the example of a device designed to work with digital circuits built on TTL elements in which possible voltages are in the range from zero to 5 V.

The signal generator 2 is a voltage source, for example, with a voltage of minus 2 V. In this case, a resistor with a nominal value of 1 MΩ can serve as a current-limiting node 1. At voltages that may be in this test object, the current through the above node should be within 2-7 μA. Since the output resistance values of TTL elements do not exceed several kOhm, this current can cause an error not exceeding several tens of millivolts, which is usually acceptable when measuring TTL elements. In this case, a voltmeter can serve as a signal meter.

During the test, in the absence of contact between the tested object and the measuring device, the signal meter 3 shows a voltage whose value is in the range of minus 2 V - zero volts. Moreover, the higher the input resistance of the measuring device and signal meter 3, the readings of signal meter 3 are closer to minus 2 V. If there is a contact, signal meter 3 can show any of the possible voltages in the range of zero - plus 5 V.

Thus, the proposed device allows to obtain information about the presence or absence of contact of the measuring device with the tested object. The presence of such information allows you to avoid unnecessary mechanical efforts that are necessary for guaranteed contact creation in the absence of the above information.

Claims (1)

An auxiliary unit for indicating the contact of the measuring device with the tested object, containing a signal generator other than existing in the measurement object, a signal meter and a current-limiting unit, the input of which is connected to the output of the signal generator other than existing in the object, and the output with the tested object, when In this case, the input of the signal meter and the output of the current-limiting unit are connected to the tested object at one point with the measuring device.

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