SU83467A1 - Electrical measuring device - Google Patents

Description

The subject of the invention is an electrical measuring device with a magnetic amplifier, designed to measure relatively small voltage values (up to 1 V) of alternating current.

Such measuring devices, known in the art, work according to the zero method or the principle of a nonequilibrium bridge.

The relative measurement error using these devices is determined by the sensitivity of the null indicator or the accuracy class of the meter, and they do not contain any devices designed to reduce the relative error and change the measurement limits.

The proposed device is an iribor.m with a direct reading without using a bridge circuit and contains the fixture g, 1: i change the relative strength and change the limits of measurement.

The device is based on the use of saturation throttling properties.

FIG. 1 shows a device diagram; in fig. 2 dependency curve; in fig. 3 error curves on a scale of 20 + 40 μA.

The bulk choke (magnetic usi, titele) 2 has four pairs of terminals, which include alternating current to the winding of the primary current (aaa), direct current to the control winding (bb), adjustable current) of the current 5Ni bias winding (v-s) and the output of the rectifier 3 to the feedback winding (yr).

The AC current connections of the throttle of the feeding of 2 are powered from the network through the stabilizer J. Consistently with it, the rectifier 3 is connected, supplying a direct current to the feedback winding of the saturation throttle 2 and a millimeter -4 DC. A choke and a winding under magnet which is supplied from a source of a constant current 6 through a current regulator 5 allow changing the magnitude of the amperes of the magnetic bias.

The control winding of the throttles 2 using the switch 8 is either output directly to the DC output terminals, or connected to the output of the rectifier 7. to the input of which gives the number 83467-2 with the measured alternating current. Rectifier 7 can be any valve device, for example a solid rectifier, an electronic lamp, a mechanical rectifier.

In the absence of node magnetization, the characteristic of the droplet, which is a curve of the dependence of the readings of milliammeter 4 on the current in the control winding, has the form shown in FIG. 2. This curve shows that with a change in the current in the control winding from 0 to 20 µA, the readings of the 4-millimeter meter change from 5 to 1.25 µA. Thus, in the absence of bias, the device allows to measure currents from 0 to 20 microns, as well. In this case, the measurements satisfy an accuracy class of 2.5 with the usual limits of variation of the voltage and frequency of the network, temperature and external magnetic fields.

Milliammeter 4 is made with zero suppressed. The milliammeter spring is shrouded in such a way that when the current in the frame is 1.25 microns, the instrument pointer is at the edge of the scale and with an increase in the current in the frame from 1.25 to 5 microns, the arrow goes through the whole scale. This achieves full use of the angle of rotation of the milliammeter frame.

As you know, when biasing the saturation throttles from an extraneous source of direct current, its characteristic shifts parallel to itself. Obviously, if the throttle is magnetized and only so that the point of 5 μA of its characteristics moves so that its abscissa becomes 20 μA, then the arrow of the milliammeter will go through the whole scale when the control current (measured value) changes from 20 to 40 μA and the device can Used to measure currents within these limits. The absolute value of the error will remain the same as it was in the previous case when measuring currents from 0 to 20 µs, while the measured velccins doubled. As a result, the relative error will be halved and instead of 2.5% occurring on the 0 + 20 µA scale, we will get on the 20 + 40 µA scale the error of 1.25 / o relative to the nominal scale value of 40 µA (Fig. 3 ).

In the same way, by increasing the magnetization, i.e., by shifting the characteristics of the throttles farther and farther by multiples of 20 microns, one can proceed to measuring increasing and large currents, respectively, reducing the relative error by as many times as many times the measurement limit on which more than twenty microamperes are measured.

The described device has 25 magnetisation stages, which makes it possible to measure currents from 480 to 500 µa with an accuracy of 0, in a twenty-fifth stage.

Thus, according to the definition of the accuracy class according to the standard, the device as a whole with the aid of the extinction bias of throttles makes it possible to measure currents from 0 to 500 μA in the accuracy class 0.1 relative to the nominal measurement limit 500 μA. With the appropriate additional resistances, the instrument can serve as a voltmeter. Essentially, an increase in measurement accuracy is accomplished by compensating for a portion of the amp worm. generated on the core of the throttles by the measured current, ampere-turn. Therefore, the accuracy class is largely determined by the accuracy of the bias current setting. The magnetization current is monitored by a device with a highly closed zero, which ensures the accuracy of maintaining the node current magnitude of the order of 0.02 / o.

The instrument's circuit provides for the installation of an arrow of the meter to the zero of the scale by adjusting the supply voltage of an alternating current alternating current circuit.