Huygen Model 615 Illumination Meter. US Man. 1968
In America, Weston Electronic Instrument Corp. was bought out by Daystrom in 1954 and then Schlumberger in 1962. The factory continued in Newark until 1974. At some time in this time span an upgraded version of the model 614 was developed: the 615. This used a PP3 9v battery inserted in the back which linked to a basic amplifier that boosted the signal from the Selenium cell. Along with a rotary switch and a shunt network, this gave the meter seven range levels from 1.2 foot candles up to 1200. The battery used also helps us narrow the time time frame a little. EverReady didn't introduce the PP3 until 1956 which means that, at the earliest, the Model 615 must have been developed under Daystrom ownership.
Whether by Weston, Daystrom or Schlumberger, examples of this model can be found on-line bearing the Weston name. The Huygen Corp. of Barrington, Illinois was established in 1968 and took on servicing and upgrading of Westons. Here the picture becomes confusing, as it's not clear if they were manufacturing the meters directly. They may have been assembling them from parts supplied by the Newark factory or they may have badged and vended meters made entirely at Newark. The pristine example in my collection here bears the name Huygen on the instructions and meter face and does not mention Weston anywhere. In every single other respect (including the instruction legend) it is identical to the Weston examples on line. I think it's made in Newark.
The back has been unscrewed and a fresh battery inserted. The signal amplifier section, rotary switch and shunt array on the circuit board are exposed. Each rheostat is adjustable and the unit has been fully calibrated and the settings sealed.
The instructions and recommended workplace lighting levels mounted on the inside of the hinged cover of the 615 Illumination meter.
An example of the 615, identical to the Huygen above, except this one does bear the Weston name. From 1973, this is badged for Schumberger, the then owners of Weston Instruments Inc.
(Notice on both of these models, the design of the range switch, which has to be returned to the 'off' position at 3 o'clock, otherwise the case would not close: a thoughtful safety and battery saving feature.)
(Right) An interesting correction table made by the user of this meter, which, as indicated, remained in use until at least 1997. It shows a considerable drift in accuracy, particularly across the upper ranges of the meter.
(Left) The back of the Schlumberg Weston 615 revealed. Notice how fixed value resistors are mounted here in contrast to the adjustable rheostats used in the Huygen model above.
