SU1564568A1 - Apparatus for determining errors of ohmmeters - Google Patents

Abstract

The invention relates to devices for determining the accuracy of analog ohmmeters, the margin of error which is normalized as a percentage of the scale length, i.e. in linear-reduced form. The aim of the invention is to increase labor productivity during the inspection and to improve the accuracy of estimating the linearly reduced error by eliminating the need for recalculation using the formula of the linearly reduced error and the associated measurement of the scale length and determining the sensitivity of an ohmmeter at a given point of the scale. The goal is achieved by counting directly on a voltmeter scale of 5 ohmmeter error as a percentage of the scale length. The first position of the pointer of the ohmmeter 1 is implemented in the second cycle by adjusting the source 3, the second position is reached in the third cycle by installing a resistance on the magazine 6 equal to the nominal value for this mark. The setting of the required conversion factor of the scale converter 4 is carried out in the first operation cycle. The proposed device can be implemented from standard components, which determines its manufacturability and low cost. 1 il.

Description

315

The invention relates to devices for determining the error of an analogue I tx ohmmeter, the limit of which is normalized as a percentage of the scale length, i.e. in linear-reduced form.

The purpose of the invention is to increase labor productivity during the inspection and to increase the accuracy of estimating the linearly reduced error by directly reading the ohmmeter error as a percentage of the scale length.

The drawing shows a device for determining the error ohmmeters.

The device contains an ohmmeter 1, the first output of which is connected via a switch 2 to the source 3 of an adjustable voltage and to the first input of a scale converter 4, the outputs of which are connected to the inputs of a voltmeter 5, while the second input of the scale converter 4 is connected to the second output of a switch 2 and through model store 6g of resistances - with outlets of an ohmmeter 1 and source 3 of an adjustable voltage.

The device operates in three cycles: calibration of a scale converter, installation of an ohmmeter pointer, determination of an ohmmeter error. In the first cycle, an adjustable voltage source 3 is connected to ohmmeter 1 via switch 2. By adjusting the voltage of the source 3, the ohmmeter needle is set at the end of the scale, by adjusting the conversion coefficient of the scaler 4, the voltmeter 5 is set to 100 units (for example, 100 mV) and corresponding to 100% of the ohmmeter error. In the second cycle, by adjusting the voltage of the source 3, the ohmmeter needle is set to the checked scale mark. In the third cycle, the model store 6 establishes a resistance equal to the nominal value of the ohmmeter scale being checked, switch 2 switches to the lower position, and the error value in percent of the scale length is counted on the scale of the voltmeter 5. After that, the switch 2 is again set to the upper position, the error is determined at the next mark of the ohmmeter pu

/

15

20

25

four

the repetition of the second and third cycles,

The principle of operation of this device is based on the fact that the linear deviation of 1 ohmmeter indicator is proportional to the current flowing through it, This current, in turn, is proportional to the difference Uoo-U, where UQ, -. the voltage at the terminals of an ohmmeter with an infinitely large value of the measured resistance, t0e0 disconnected terminals; U is the voltage across the ohmmeter terminals when a measured resistance is connected to it, Thus,

1 kt (U№-U), (1) where k, is the proportionality coefficient;

Obviously, when t0e, with shorted clips, the pointer moves to the full scale length, from where

(2)

Of

k L.

1 iodine

expressions & l k.alJ.

(1) follows

(3)

where / 31 is the ohmmeter error, expressed in units of the scale length;

#U is the voltage change at the ohmmeter terminals that causes the pointer to move to D1 .. The voltage U measured by the voltmeter 5 is related to the ratio

U, (4)

where k is the conversion factor of the scale converter. Considering that, by definition, the linear reduced error is v

D1

100 and taking into account (1),

0

five

five

(2), (3), (4), we obtain

T (U / k Uj-lOO,

100

When K --- expression gets

/

view - u, i.e. The readings of the voltmeter 5 are numerically equal to the linearly reduced error. To determine P1), it is necessary to find the voltage difference at the terminals of the ohmmeter pr and the two positions of the pointer: at the checked scale mark and at the point where the pointer will be when connecting a resistance equal to the nominal value of the checked mark The first position of the pointer is realized in the second cycle By adjusting the source 3, the second position is reached in the third cycle by installing an exemplary resistance 6 on the model magazine equal to the nominal value for this mark. The setting of the required ke coefficient is made in the first cycle of operation.

The use of a device for determining the error of ohmmeters allows to significantly simplify the procedure of verification due to the fact that the linearly reduced error, i.e., the error, expressed as a percentage of the scale length, is measured directly from the voltmeter included in the installation. This eliminates the need for time-consuming measurements of the geometric dimensions of the scale and in terms of absolute error in the linear-reduced. This simultaneously achieves an increase in the accuracy of determining the error, reduces the number of verifiers due to increased productivity, This device can be implemented from standard components,

which determines its manufacturability and low cost.

Claims (1)

Invention Formula A device for determining the error of ohmmeters, which contains a circular resistance box, the first terminal of which is connected to the first terminal of an ohmmeter, so that, in order to increase labor productivity during the test and increase the accuracy of the linear-reduced error, the first terminal of an exemplary resistance box connected to the first pole of the variable voltage source, the second pole of the variable voltage source and the second terminal of the exemplary store of correspondences bonded through scale converter to the input of the voltmeter, and by switch - with the second terminal ommetrao