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HP 3403A/B/C (Thermopile 0853-0014) What is it?
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ocklawaha:
Hello everyone! My first post on EEVBlog!
I got my hands on an old HP 3403A RMS Voltmeter. Amazing little instrument design.
She powers up on the bench fine. The 70's LED displays all work and controls seemed responsive.
Trouble came in on the actual input test. The AC function doesn't read. DC input no issues.
On tear down, I believe I located the culprit. It has what HP called at the time TCIa/b THERMOPILE (HPPart#0853-0014). It is a custom component from HP. I can't find any data on this can.
If anyone has a datasheet or even a description for that matter, it would be much appreciated.
Here are a few links to photos of the piece and associated circuitry.
https://postimg.cc/gallery/32dc5pN
Thanks!
Mitch
TimFox:
A thermopile is a series connection of thermocouples (to increase the voltage). Thermal rms meters work by heating two matched thermocouples/piles: the input voltage heats one (through a heating element resistor) and a servo heats the other to produce the same thermal emf. Measuring the dc voltage on the second heater (when the servo balances the two temperatures) yields the rms value of the input, since the two power values are equal. It would be very difficult to fabricate a replacement.
appsman:
I know this post is 3 years old, but I found it while researching the HP 0853-0014. I found some in a pile of parts. I have these devices if you still need them (for cost of postage only). Contact me if you can still use them.
doktor pyta:
https://www.eevblog.com/forum/testgear/hp3403c-marvels-(photos)/msg3349034/#msg3349034
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