Inside a melting point apparatus
I bought a Mel Temp 3.0 a while ago for <$50 at auction. They usually go for $200-400 although you still see some clowns listing them at $800-1200.
It's a nice instrument to have but I wondered why it was so expensive. It must be some crazy high tech shit inside, right?
https://imgur.com/a/BmFVppJ
The large cylindrical tube at the front projects light into the aluminum heating block. The heating block has 3 holes on top for capillaries, and two
holes on the bottom for dual PT100 RTDs. The heating element is the bent metal piece sitting above the heating block. Rapid cooldown is enabled by the
12V DC fan you see to the side of the heating block.
You can see the manual to the PID controller here, if you're curious. It's not some special scientific grade controller, it's just ordinary process
grade PID controller. https://www.watlow.com/-/media/documents/user-manuals/988ev.... The model number used in the apparatus supports a PT100 RTD (more accurate than
thermocouples) and it looks like that's what's going on here. I believe they're using the dual PT100 probes in a limit/process configuration shown in
"Dual PID Sets" section of the manual.
Anyways, I thought it was interesting. You could probably get 90% of the accuracy with an Arduino controller using type K thermocouples like aga did
here: http://www.sciencemadness.org/talk/viewthread.php?tid=32018 A proper PT100 RTD setup could be done for not much more with something like a
MAX31865 breakout board and some Chinese PT100 RTDs.
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