Measuring instrument for short-circuited coils. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Measuring device for short-circuited coils. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Measuring technology

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Short-circuited turns in the coils of a horizontal transformer, in deflecting coils, etc. are very difficult to detect. For these purposes, you can use the short-circuited turns meter, the schematic diagram of which is shown in the figure.

Transistor T1 together with coil L1 and capacitors C1, C2 forms a capacitive feedback generator. Transistor T2 has a voltmeter that measures the amplitude of the generated signal. Resistor R7 limits the collector current of transistor T2. When a working coil is connected to the input of the meter, the readings of the measuring device should practically not change. If there are short-circuited turns in the coil, the quality factor of the oscillatory circuit decreases and the instrument readings decrease.

Shorted winding meter

The procedure for setting up the meter is as follows. Before turning it on, the engine of the variable resistor R2 is set to the lower position, according to the diagram. Then turn on the power. The collector current should be about 0,1 mA. By moving the variable resistor slider up. achieve self-excitation of the generator. the collector current of the transistor in this case will jump up to about 0.4 mA. When the input sockets are short-circuited, oscillations should stall (this will be indicated by a decrease in the readings of the milliammeter).

The sensitivity of the device is checked by creating short-circuited turns on a working coil.

The meter can use transistors such as KT312, KT315.

Literature

"Radio Electronics" (USA). No. 1, 1974

Publication: N. Bolshakov, rf.atnn.ru

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