A similar device (see figure) can be constructed on the arrow indicator from old reel-to-reel tape recorder. The role of sensor in it performs field-effect transistor VT1, forming, together with the resistors R1 and R2 of the voltage divider to which the connected indicator PA1. When increasing the electric field around the antenna WA1 the channel of the source-drain field-effect transistor is narrowed and thereby increases the voltage on the display. The greater the angle of deflection of an arrow, the intense field.

The field indicator

For normal operation of the indicator requires a supply voltage of 1.5 V - this can be a element 316 or storage battery D-0.26. Field-effect transistor - any of the series K, K, resistors - power from 0.125 watts. Antenna to serve cut copper wire length of 5 6 see...the Switch - any small-sized.

Establishing device is reduced to the selection of the resistor R1 that value to in the absence of the field the meter needle was at the starting point of the scale.

The indicator can be used as a finder of hidden wiring or malfunction of Christmas garlands.

Author: A. Petrovsky, Uralsk West Kazakhstan reg.

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