1863
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The GR Type 1863 Megohmmeter was introduced in Catalog U (1970). It is still available from IET Labs as of 2024.
Specifications
- Test Voltage: 50, 100, 100, 250, or 500 V; 5 mA limit
- Resistance Range: 50 kΩ 20 20 TΩ in 7 ranges
Links
- The Type 1864 Megohmmeter is similar but with a 200 TΩ top range, and test voltage variable from 10 V to 1090 V.
Internals
The 1863 is solid-state except for the test voltage supply pass element, a 6AB4 (EC92) vacuum tube.
Current through the unknown is converted to a voltage using decade reference resistors from 2 kΩ to 200 MΩ. In the highest range (1 TΩ multiplier), feedback is used to multiply the effective reference resistance by a factor of 10.
A four-stage, FET-input amplifier drives an analog meter.
