22 December 2016

My first Nixie-based instrument

At the ARI Torino HAM rally few Sunday ago (Nov, 27th 2016) during my third or fourth tour of exhibitors I spotted what looked like a box with Nixies. The box read "Philips PM2422". A quick picture search with the smartphone confirmed my suspicions: a 3 and half digit multimeter, with Nixies. I was even able to power it up right there, and the tubes happily glew.
I paid 30€ and I think it was the right price. The seller then realized he could have asked more, I nodded and I replied that I did not negotiate the price on purpose.
Once home I opened it, and everything looked fine. No fat electrolytics, no sign of burns. But a surprise: there are only three tubes inside, not 4 or 4+1 as in the PM2421. The most significant digit is a long neon lamp, so there's implicit leading zero blanking. And the minus sign is another small neon lamp. That's it. Cheaper than full feature tubes but effective. I think more recent versions of the same instrument carry four tubes. I got a PM2422/A2, while they went up to /A5.
Finally I own a bench multimeter!
Oh, by the way, can it be a clock? Well, it can count from 0 to 1999, so as a 24h clock it would work up to 19:59. It is suitable as an office desktop clock since most people leave way before 8 pm. Or simply make it a 12h clock. I want to explore if a simple DAC produces a stable enough reading, soon.