Digital Test
Weston 1294

Manufacturer: Weston
Model: 1294
Year: 1970
Schematic: RE
Functions: DCV
Display: NIXIE
Digits: 4.5
Logic: TTL

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.

- Unit Log -

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