Electronics > Projects, Designs, and Technical Stuff

put component into oil-filled "can".

(1/4) > >>

I want to make a heated zener reference (I know I can buy them, but I want to make it).  My plan is to put a zener, NTC, into a metal "can", fill it with oil, and attach a heater (resistor) to it. 

I can do this by machining something, adding a gasket and screwing it down.  Before I do anything stupid or overly complicated though, I'm wondering if anyone has already done something similar and how they accomplished it.

Any tips tricks links would be appreciated. 

Check out the Metrology section, you may find something there.

Thoughts that come to mind...

- You want to use medical grade liquid paraffin as the oil (there's certainly a discussion on that in Metrology).
- Your main enemy is probably convection currents and hotspots. Oil filled calibration baths normally include a stirrer. Relative positioning of Zener, thermistor and resistor are probably important.
- You might achieve better results by machining a solid Aluminium (or better, Copper) block with pockets and thermal compound coupling for the zener and thermistor as well, either in the oil can or standalone. ie. Keep the thermistor and zener as closely thermally coupled as possible.

Thanks for the input!

I searched metrology but didn't find much, but I do find searching this forum kinda hard so maybe I missed something.

For my current plan:
I have the zener and NTC both in DO35 packages and I plan to lay them out symmetrically with the "can"(1) itself heated by a to92 to-220 resister in the center, hopefully spreading the heat evenly or at least symmetrically between the two.  IDK what size scales convection matters.  the cavity is probably going to be in the range of 12x6x6 mm.

(1): I can't really fabricate a can so it'll be an alu or brass block with a pocket and a gland around it for a gasket.

since its electrically heated and filled with oil, you should put a weak point on it so it does not accidentally pressurize itself with hot oil. It should be designed to pop a seal with over pressure in a safe way. I see the real oil standards are often open or just have a loose lid on the top, but they are basically like crock pots. It seems like something bad could happen if you have a prolonged overload followed by a really heavy transient, but unless its hooked directly into mains I dunno if its a concern.

On the other hand beware of oil leaking and hurting you with an oil slick, since its a home made container.

In theory you can use oil, in practice can be messy, but it all depends at what you want to use the final voltage for.

AFAIK normal Zener diodes are noisy to be used as a metrologic voltage reference (between other disadvantages).  There are quite a few threads about voltage reference and thermal stabilization, e.g. this huge one:

By the flag you are from US, should be plenty of cheap spare equipment on ebay where you leave.  You can find a metrology reference pile, or an old voltage reference module from a retired lab, or from former military equipment, etc.

For amateur grade reference, maybe you won't get much advantage from oil, a radiator coupling in a small thermally isolated can might do as well as the oil filled can you want to build, but I have no hands on experience with this.  Better set some specs you aim at, then ask for advice in the metrology section.


[0] Message Index

[#] Next page

There was an error while thanking
Go to full version