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General Radio 546-C
Audio-Frequency Microvolter
General Radio 546-C Audio-Frequency Microvolter

Available from 1948 to 1968

Catalog History
 Document Year Page
Catalog L 1948 158
Catalog M 1951 182
Catalog N 1954 190
Catalog O 1956 135
Catalog P 1959 133
Catalog Q 1961 131
Catalog R 1963 24
Catalog S 1965 38
Catalog T 1968 48
(All manuals in PDF format unless noted otherwise)

The General Radio 546-C Audio-Frequency Microvolter was introduced in Catalog L (1948) and remained available through Catalog T (1968).

It is an audio-frequency voltage divider and attenuator, an updated version of the earlier 546-B with changes being improvements to the meter, and adoption of the 600 Ω impedance standard for audio applications.

The primary application of the 546-C is to supply audio-frequency voltages at attenuated and calibrated levels, but it can also be used to measure unknown voltages by "Substitution" and "Insert-Voltage" methods.

Any audio oscillator that can supply 2.2 V into 600 Ω will be sufficient to drive the Microvolter.


  • Output Voltage Range: 0.5 μV to 1.0 V, with 2.2 V input voltage
  • Accuracy: For open-circuit output voltages, calibration is accurate within ±(3% + 0.5 μV) for output settings above 1 μV and for all frequencies between 20 and 20,000 Hz
  • Output Impedance: approximately 600 Ω ±5%
  • Input Impedance: approximately 600 Ω