SU113189A1 - Device for changing the limits of measurement of electrical measuring devices - Google Patents

Description

In electrical measuring technology, auxiliary devices in the form of shunts (for current meters) or additional resistances (for voltage meters), as well as various devices for switching measurement limits in circuits that work on the principle of compensators, are often used to expand the limits of measurement.

Manual switching of measurement limits is completely unsuitable for automatic recording of their instruments, since the need for the presence of the operator, the trace, his change of limits and production, his operation, contradicts the very principle of automation.

To automatically change the limits of measurement of devices in accordance with the values of measured currents or voltages, it has been proposed to use devices containing two photoelectric relays installed at the ends of the scale and controlled by the pointer at its maximum deviations.

The proposed device is more perfect in comparison with the known devices of this kind, since it provides an automatic multiple change of the measurement limits of the device, both in the direction of their increase and decrease.

This is achieved by the use of an electromagnetic step switch, controlled by the indicated photo relays. One of these relays serves to switch the instrument circuit to a larger measurement limit with a maximum deviation of its pointer. The other relay triggers at a predetermined minimum deflection of the indicator and turns on the switch winding to its self-driving contacts, through which circuits form to switch the switch to its initial condition corresponding to the smallest measurement limit of the instrument.

The drawing shows a schematic diagram of the proposed device.

The device contains semiconductor photoresistances 1 and 2,

light bulbs 3 for illuminating the photosensitive elements of photoresistance, polarized two-winding relays 4 and 5, step finder and small 6 and 7. Power is supplied to all elements from transformer 8 through semiconductor rectifiers.

Photoresistance / is connected in series with the windings of a polarized relay 4, the contacts of which act on the power supply circuit of the stepper finder coil and control the movement of its brushes along the contact field.

Each time the short circuit of the relay 4 with its lower contact causes the movement of the seeker brushes one step (contact) necessary to go from the lower measurement limit of the device to the higher. self-propelled 10. These contacts control the self-propelled movement of the finder's brushes during the switch from the highest measurement limit of the instrument to the lowest.

The step finder performs the following functions:

a) contact field // supplies power to the searcher's self-propelled circuit, ensuring that it stops at the 1st contact (i.e., leads to c: its initial state);

b) contact zero 12 provides alternate operation of relay 7, which with their cores beat off marks on the recorder tape, indicating which measurement limit is currently on;

c) the contact field 13 provides alternate operation of the relay 6, which by their contacts switch the shunt 14, additional resistance or other circuit elements that change the measurement limits of the device.

Photo-resistors / and 2 and bulbs 3 are fixed on a scale of 15

measuring device. When the pointer 16 is positioned at the left support, the flag 17 overlaps the light beam incident from the light bulb 3 on photoresistance 2, and when it is located at the right stop, the flag 17 blocks the light beam incident on the photoresistance /. This achieves contactless control of switching the measurement limits of the instrument.

With this control method, the mobile system of the measuring device does not carry any additional mechanical load, which contributes to an increase in the quality and accuracy of the device, and also does not create the sparking inherent in conventional switches with electrical contact.

The inclusion of the device in the network is made by a toggle switch 18; protection against short circuits and long-term overloads is carried out by a fuse 19.

The capacitors 20 serve to smooth out the pulsations of the rectified current, which is necessary for the accurate operation of the relay and the coil of the step finder.

The proposed device operates as follows.

When the pointer reaches the limit of the scale. relay 4 is activated and acts on the coil of the 9-step finder. The contacts of the latter switch shunts or additional resistances to a higher measurement limit. When the indicator deflection decreases and as it approaches the beginning of the scale, the relay 5 is activated and switches on the coils of the step switch to its self-propelled contacts, which transfer the switch to the initial position corresponding to the smallest measurement limit.

Subject invention

A device for changing the measurement limits of electrical measuring devices, in accordance with the values of the measured current or currents, containing two photoelectric relays installed at the ends of the scale and controlled by the pointer at its maximum deviations, characterized in that the limits of measurement of the device, both in the direction of their increase and decrease, an electromagnetic step switch is used, controlled by means of the indicated photo relays, which serve one to circuit device for prison for a longer limit at each measuring its maximum deflection indicator and the other (at its predetermined minimum deflection) -dl incorporation coil switch on its contact creep, effected guide transfer switch to the original position corresponding to the limit naimenschel1u measuring instrument.

12-1

l - measuring unit