Expansion of measurement limits Ts435. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Expansion of measurement limits Ts435. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Measuring technology

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Surely many radio amateurs have preserved the Ts435 avometer. produced by the plant "Elektroizmeritel" in Zhytomyr. For many years I have been using this device to check and adjust a variety of radio equipment and household appliances. During this time, I was convinced that the device is reliable and durable thanks to a well-thought-out scheme and solid manufacturing.

However, the avometer has a drawback, which is noticeable today. If, when measuring direct current, external shunts can be connected to it, expanding its limit to 10, 20 or more amperes, then this is not provided for alternating current and the measurement limit is limited to a maximum value of 2.5 A. In everyday life, devices with a power of more than 1 kW are sometimes used. the current consumption of which needs to be controlled.

My analysis of the electrical circuit of the avometer led to the conclusion that it is possible to simply refine the Ts435, which will expand the measurement limit of alternating current to 12,5 A.

Expansion of measurement limits Ts435

In the device (a fragment of the circuit from the instructions for the device is shown in Fig. a) there are two series-connected shunts (resistors R1, R2) from a wire with a diameter of 1 mm with high resistivity. Shunt resistance R1 - 0,072 Ohm, R2 - 0,288 Ohm. They are used when measuring alternating current at a limit of 2,5 A (only R1 “works” on direct current). Contacts 11 V and 9 A belong respectively to the switches of the type of work and measurement limits.

Modification of the avometer is reduced to the conclusion of a conductor 7 ... 10 cm long and 1 mm2 in cross section (for example, brand MGShV) from the connection point of the shunts and connecting it to an additional clamp "~ ╡ 12,5 A" - it can be mounted on a metal corner attached to the body of the meter.

The measured current is passed through this terminal and "*". In this case, the type of work switch B must be in the "~╡" position, and the switch A must be in any position. If the measured current exceeds 2,5 A, the measurements should be carried out very quickly so that the resistor R1 does not burn out.

Unfortunately, the mounting density of the avometer is such that it is difficult to get to the connection point of the shunts. I had to use a little trick so as not to break the soldering of the shunt leads with copper. I unscrewed four M3 screws from the bottom of the avometer housing. disconnected both parts of the case, unscrewed the same number of M4 screws that fasten the textolite board with the elements placed on it. Then he raised it a little and soldered the end of the new wire to the contact with conditional number 9 (Fig. b). It belongs to switch A (it has six pairs of contacts in the left row and seven pairs of contacts in the right), and a wire from the desired connection point of the shunts is connected to it inside the device.

Then he lowered the board, fixed it with three screws, except for the top left one, and led the other end of the wire into the resulting through hole. In addition, to output the wire, I had to make a small cutout in the bottom cover on the side above the galvanic cell.

Author: E. Shenderovich, Klimovsk, Moscow Region

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