SU241533A1 - METHOD FOR AUTOMATIC TESTING OF ELECTRIC MEASUREMENT DEVICES - Google Patents

Description

The known methods of checking electrical measuring instruments are based on measuring the difference in the input signal applied to the instrument being checked, and the reference signal corresponding to the scale being checked, when the midpoints of the pointer and the gauge are shifted.

When calibrating drivers with a light reading, the moment of combining the means of the pointer and the mark is determined by calculating the width of the pointer and the mark according to the preliminary measurement and their mutual approximation over a known time interval. Its accuracy is limited due to the inconsistency of the speed of the pointer.

The peculiarity of the proposed method is that in order to improve the accuracy of the calibration, the difference is measured twice - at the moment of combining the edges of the pointer and the scale mark being checked first when they are cleared: after TeiM when removed, and the result of calibration is determined as the arithmetic average of two measurements.

FIG. I shows on an enlarged scale the scale mark 1 and the pointer 2 in two positions corresponding to the measurement moments, and the graphs of the input / 7 and reference voltage voltages and their differences Af / i and Di2 at the indicated time points; in fig. 2 - simplified functional diagram

devices for automatic calibration of electrical measuring instruments.

As can be seen from FIG. 1, the difference at the time of passing the middle index

The calibrated mark (i.e., the error of the instrument) is equal to the arithmetic average of two measurements, & Ui and AL2, made by combining the edges of the pointer and the mark to the left and right of the mark. Strictly speaking, this is justified on the assumption that the scale of the instrument is linear within the interval (/ in - | - y) between two dimensions, where 0 V is the width of the mark and pointer, respectively. This interval is small, therefore

This nonlinearity is negligible for devices of any type and accuracy class. Measuring the speed of the input signal does not cause measurement errors, so the KNK with the condition of linearity of the scale in the specified interval, the average (between two measurements) position of the pointer always corresponds to the arithmetic average value of the input signal at the time of measurement. As an example of the implementation of the proposed method, we consider the functional

automatic calibration device diagram

electrical measuring instruments (see Fig. 2).

The scale of the test instrument 3 is in

The NEC 6 of the reference signal is connected to the inputs of the subtractor 7. The output of the subtractive device is connected via a switch 8 to the input of the measuring device 9. The output of the reading device 4 is connected to the input of the device 10 for determining the coincidence of the edge of the pointer and the mark, and the output of the latter to the control input // key 8. The output of the measuring device 9 through the trigger 11 is connected to the input of the counter 12.

The device works as follows.

In the initial state, the indicator of the device being checked 3 is aligned with the zero mark of the scale and is in the field of view of the readable, cro 4 device 4. Under the action of continuously increasing voltage generated by the input source 5, the indicator of the device being checked begins to move along the scale. The reader, moving along with the pointer, converts the image of the pointer and scale marks into electrical impulses. In accordance with this, the reader must contain an ootic-electronic tracking system, an electronic transducer, a device for extracting the pointer pulse and the pulse of the scale closest to it.

The device 10 for determining the alignment of the edges of the pointer and the mark generates control signals that open the key 8 when the edge of the pointer pulse coincides with the edge of the pulse of the mark first at approach and then at removal of these pulses relative to each other. Such a device can be made, for example, in the form of a coincidence circuit, fixing the moment of the merging of two pulses into one n of their subsequent separation.

Therefore, for each calibrated mark, the difference signal - t / on will be measured twice by the measuring device 9. Measurement results, expressed

in digital form, arrive at trigger 11, dividing them into two. Counter 12 summarizes the results. Thus, the arithmetic average of these two results is recorded in the counter, i.e., the accuracy of the instrument to be tested 3 at this verifiable point.

The proposed method allows to increase the accuracy of the calibration, at the same time the calibration equipment is significantly con fi ned, since

there is no need to use a computing device to determine the combination of the middle of the pointer and the calibrated elevations of the scale.

Subject invention

The method of automatic calibration of electrical measuring instruments by applying and continuously checking (decreasing) input signal acting on the instrument pointer to the calibrated instrument, determining the moment of combining the pointer with the calibrated marks of the scale and measuring the difference between the input and reference signals corresponding to those moments, differing from that, in order to improve the accuracy of verification, the difference measurement is carried out twice - at the time of combining the edges of the pointer and the calibrated mark of the scale, first when approach, zatem. when removed, and the result of calibration is determined as the arithmetic average of two measurements.

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