1212-A

The General Radio 1212-A Unit Null Detector was introduced in Catalog N (1954) and remained available through Catalog T (1968).

The Type 1212-A Unit Null Detector a wide band logarithmic amplifier used to indicate a balance during bridge measurements. It uses three stages of amplification that are designed to reduce gain as the signal increases. The output of the last stage is available at the rear panel and internal vacuum tube voltmeter displaying relative signal strength. The 1212-A null detector is recommended for use with Type 716-C Capacitance Bridge, Type 1661-A Vacuum Tube Bridge, Type 916-AL R-F Bridge, Type 716-CS1 Capacitance Bridge, and the Type 1606-A R-F Bridge at frequencies below 5 MHz. Frequency coverage can be extended to 60 Mc and sensitivity improved by the use of the Type 1212-P3 RF Mixer ahead of the null detector. The 1212-A requires an external unit power supply, the Types 1203-B or 1201-B unit power supplies are recommended. There are two accessory filters available, the Type 1212-P1 High Pass Filter for hum and noise reduction and the Type 1212-P2 One Megahertz Filter for use with 716-CS1.

Specifications

• Frequency Response: 50 Hz to 5 MHz
• Sensitivity: 40 μV at 1 kHz sensitivity for 1% deflection
• Hum and Noise Level: Hum 20 μV; broad-band noise 30 μV

Links

• Experimenter October 1953 describing Types 1212-A and 1212-P1
• Experimenter January 1956 describing Type 1212-P2

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