Digital test equipment such as counters and DVMs may not be as much fun as computers, but they constitute some of the few remaining pieces of digital electronic equipment from the 1950's and 1960's. Such equipment can be found encompassing all the generations of digital electronics from tube to IC. Some of these instruments also provide examples of the strange technologies (from today's perspective) that were developed as alternatives to tubes or discrete transistors, such as trochotron and dekatron counter tubes.

In the 1950's and 60's digital counters and DVMs were very expensive and high-tech instruments, consequently most were built to a very high standard. It wasn't until the early 1970s with the advent of lower cost integrated circuits and display technologies that such equipment came down in price and more accessible.

Most of the instruments presented here use NIXIEs for display. There has been quite a craze for NIXIEs the last few years (ca. 2007) and I wonder how many instruments such as these are being destroyed for the NIXIEs. I like to give NIXIES some period context by keeping intact some of the original equipment that used them.

Schematics for most of these instruments are available; in the model data "MF" means manufacturer's schematic, "RE" indicates the schematic was derived through reverse engineering.

Other Sites

• [R] Kenneth Kuhn's list of HP equipment presents some more info about the 520 models.
• [R] The HP Archive site provides scans of early HP catalogs.
• The HP Memory site presents more history of the origins of the 520 series, and has a 524D and 521C.
• Stefan Graef's Museum of T&M Instruments has a 524C.
• SMECC's history of HP also has some mention of the development of the 524.
• Nixiegear presents some NIXIE test equipment.