Field indicator. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Field indicator. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Beginner radio amateur

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A similar device (see figure) can be built on a dial indicator from an old reel-to-reel tape recorder. The role of the sensor in it is performed by a field-effect transistor VT1, which together with resistors R1 and R2 forms a voltage divider, to which the indicator PA1 is connected. With an increase in the electric field around the WA1 antenna, the drain-source channel of the field-effect transistor narrows and thereby increases the voltage on the indicator. The greater the angle of deviation of its arrow, the more intense the field.

Field indicator

For normal operation of the indicator, a 1,5 V power supply is required - this can be an element 316 or a D-0,26 disk battery. Field effect transistor - any of the series KP302, KP303, resistors - with a power of 0,125 W. A piece of copper wire 5 ... 6 cm long can serve as an antenna. The switch can be any small-sized one.

Setting up the device comes down to selecting a resistor R1 of such a value that, in the absence of a field, the indicator needle is at the initial mark of the scale.

The indicator can be used as a searcher for hidden electrical wiring or a malfunction of the New Year's garland.

Author: A. Petrovsky, Uralsk, West Kazakhstan region.

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