Industrial panel meters made the transition from analog to digital in the early 1970's. This is one of the few NIXIE-display models produced before such instruments settled in to the use of LEDs for display.
The A-to-D converter is of the dual-slope integration type, implemented with discrete and SSI components. The design impressively achieves this with a relative paucity of components, and packed into a small form factor.
The native range of the design is +/- 200.0 mV, auto-polarity is included.
Model options allowed for internal input configurations for other voltage and current ranges.
Overflow is indicated by a flashing of the display.
Bottom of case showing model options.
Analog / upper board with power supply and input amplifier.
Digital / lower board with integrator, counter and display.
|Serial Number: ||73902|
|Year of Manufacture: ||1970 (IC date stamps of 7011 to 7039).|
|Date of Receipt: ||2006|
|State upon Receipt: ||OK physically, a little shaky functionally.|
|Date: ||2006 Mar|
|Procedure: ||Cleaned. RE'd.|
|Date: ||2006 Mar 27|
|Symptoms: ||Socket pin for DP of LSD will not accept tube pin.|
|Procedure: ||Socket pin removed. A couple of other pins have intermittent contact.|
|Date: ||2008 Mar 07|
|Symptoms: ||Display does not light up.|
|Procedure: ||Anode supply not present. Secondary of transformer is open. Break in fine wire of secondary found on top of windings near where it connects to more-solid lead. Managed to scrape enamel off and get a lead extension to solder to it. Resistance now measures around 2.2 or 3.3 K.|
|Date: ||2015 Nov|
|Procedure: ||Design analysed, noted to be dual-slope integration.|
.. | Weston 1294 | ..
Early Digital Test Equipment