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General Radio 1650-A
Portable impedance bridge
Genrad 1650-A Bridge

Available from 1959 to 1967

Catalog History
 Document Year Page
Catalog P 1959 24
Catalog Q 1961 22
Catalog R 1963 34
Catalog S 1965 50
(All manuals in PDF format unless noted otherwise)

The General Radio 1650-A is a portable impedance bridge introduced in Catalog P (1959). It was succeeded by the 1650-B in Catalog T (1968).

The 1650 was the first GR impedance bridge to feature the "Orthonull" function, which is a mechanical link driving the DQ dial from the CRL dial through a friction clutch. (Conversely, turning the DQ dial will not turn the CRL dial.) It helps avoid the "sliding null" problem when measuring components with high losses.

The 1650-P1 Test Jig accessory was designed for the 1650-A.

Key Specifications

  • Capacitance: 1 pF to 1100 μF in 7 ranges
  • Inductance: 1 μH to 1100 H in 7 ranges
  • Resistance: 1 mΩ to 11 MΩ in 8 ranges, AC or DC
  • D (of series capacitance): 0.001 to 1 at 1 kHz, (parallel capacitance) 0.1 to 50 at 1 kHz
  • Q (of series inductance): 0.02 to 10 at 1 kHz, (parallel inductance) 1 to 1000 at 1 kHz
  • Basic accuracy: ±1% of full scale, ±5% for dissipation factor
  • Internal oscillator: 1 kHz ±2%
  • Frequency range: 20 Hz to 20 kHz (to 100 kHz with reduced accuracy)
  • DC Supply: 6 V, max. 60 mA; Battery: Four D cells, current drain 10 mA (AC measurements)
  • External Oscillator and Detector: Type 1210-C Unit R-C Oscillator, Type 1311-A Audio Oscillator and Type 1232-A Tuned Amplifier and Null Detector are recommended for audio measurements at frequencies other than 1 kHz
  • DC Polarization: 600 V may be applied (from external source) for series capacitance measurements
  • Weight: 17 pounds (8 kg) net