Section IV. THEORY OF OPERATION

THEORY OF OPERATION

4.1 An understanding of the operating features of the RF Volt-

meter may be obtained by a study of the block diagram (Fig. 5)

in conjunction with the following description.

The radio frequency voltage to be measured is recti-

fied in the RF Probe by means of a full wave germanium diode

rectifier circuit. The resulting DC potential is then attenu-

ated as required before conversion to 60 cycle AC by the chopper.

This AC signal is then amplified in a narrow band feed-back

stabilized amplifier prior to its re-conversion to DC for use in

actuating the meter.

The germanium diodes used in the RF Probe have been

carefully selected for several characteristics. As the selected

diodes do not all exhibit the same rectification efficiency

characteristics, it becomes necessary to adjust each meter range

to match individual probe diodes. The range adjustments consist

of individual non-linear circuits shunting the output meter

circuitry. As the RANGE switch is set to the required test volt-

age position the appropriate non-linear adjusting circuit is

automatically shunted across the output. It is also important to

understand that the non-linear output circuitry is designed to

compensate for the non-linear characteristics of the probe diodes

when operating at levels below 0.3 Volt.

BLOCK DIAGRAM OF RF VOLTMETER

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