1864: Difference between revisions

Latest revision as of 20:22, 27 August 2024

General Radio 1864

Megohmmeter

Available from 1970 to the present day

Manuals

Catalog History

Document	Year	Page
Catalog U	1970	98
Catalog73	1973	182

(All manuals in PDF format unless noted otherwise)

The GR Type 1864 Megohmmeter was introduced in Catalog U (1970). It is still available from IET Labs as of 2024.

Specifications

Test Voltage: 10 V to 109 V in 1 V steps, 100 V to 1090 V in 10 V steps; 5 mA limit
Resistance Range: 50 kΩ to 200 TΩ in 8 ranges
Power: 100-125 or 200-250 V_AC, 50-400 Hz

Links

The Type 1863 Megohmmeter is similar but with a 20 TΩ top range, and a choice of only five test voltages (50, 100, 100, 250, or 500 V).

Internals

The 1864 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 2 GΩ.

In the highest range (10 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 that is unusual in that its mechanical zero position is on the right end of the scale.

Photos

GR-1864 schematic

@@ Line 8: / Line 8: @@
 |series=
 |introduced=1970
-|discontinued=current
+|discontinued=the present day
 |designers=
 |manuals=
 * [[Media:GR 1863 and 1864 Instruction Manual 1863-0100-00.pdf|GR 1863 and 1864 Instruction Manual (1863-0100-00)]]
+* [[Media:GR 1863 and 1864 Instruction Manual 1863-0100-B 1973-03.pdf|GR 1863 and 1864 Instruction Manual (1863-0100-B, 1973)]]
 * [[Media:GR 1863 and 1864 Instruction Manual 1863-0100-C 1974-08.pdf|GR 1863 and 1864 Instruction Manual (1863-0100-C, 1974)]] (readable schematics)
 * [https://www.ietlabs.com/pdf/Manuals/1863-64_im.pdf GR1863/1864 Instruction Manual, Aug 2018] @ IET Labs
+* [[Media:GR-1863 and GR-1864 stitched schematics.pdf|GR-1863 and GR-1864 stitched schematics]]
 {{Catalog History}}
 }}
@@ Line 20: / Line 22: @@
 ==Specifications==
 * '''Test Voltage:''' 10 V to 109 V in 1 V steps, 100 V to 1090 V in 10 V steps; 5 mA limit
-* '''Resistance Range:''' 50 kΩ 20 200 TΩ in 8 ranges
+* '''Resistance Range:''' 50 kΩ to 200 TΩ in 8 ranges
+* '''Power:''' 100-125 or 200-250 V<sub>AC</sub>, 50-400 Hz
 ==Links==
-* The Model [[1863]] is similar but with a 20 TΩ top range, and a choice of only five test voltages (50, 100, 100, 250, or 500 V).
+* The [[1863|Type 1863 Megohmmeter]] is similar but with a 20 TΩ top range, and a choice of only five test voltages (50, 100, 100, 250, or 500 V).
 ==Internals==
-The 1864 is solid-state except for the test voltage supply pass element, a 6AB4 (EC92) vacuum tube.
+The 1864 is solid-state except for the test voltage supply pass element, a [[tekwiki:6AB4|6AB4 (EC92) vacuum tube]].
-Current through the unknown is converted to a voltage using decade reference resistors from 2 kΩ to 2 GΩ.  In the highest range (10 TΩ multiplier), feedback is used to multiply the effective reference resistance by a factor of 10.
+Current through the unknown is converted to a voltage using decade reference resistors from 2 kΩ to 2 GΩ.
-A four-stage, FET-input amplifier drives an analog meter.
+In the highest range (10 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 that is unusual in that its mechanical zero position is on the right end of the scale.
 ==Photos==
 <gallery>
 GR-1864-1.jpg
+GR-1864-7.jpg
 GR-1864-2.jpg
+GR-1864-8.jpg
 GR-1864-3.jpg
 GR-1864-4.jpg
 GR-1864-5.jpg
 GR-1864-6.jpg
+GR-1864-schematic.jpg | GR-1864 schematic
 </gallery>
 [[Category:Meters]]
 __NOTOC__