Mike W1
09-17-2015, 05:12 PM
Been fooling around with PID's, TC's, and closures to limit heat loss for last couple of weeks and have concluded just like he said it ain't all necessary. All you need is the hot plate! But keep in mind I was having fun and these weren't scientifically precise tests. At best gonna be approximations. Now what I learned.
l. Stem dial thermometers react slowly immersed in lead. They're even slower just exposed to air.
2. Even 1/8" TC probes react pretty slowly in air.
3. Realistically with a PID controlling either the contact screw-in TC and the 1/8" probe in the air could control the hot plate temperature within ± 2-3° F.
4. With the air sensor you had a constant off/on surges of power to the hot plate.
5. The mounted TC didn't ever do that for me.
6. Using the mounted TC and the Mypin just as a thermometer, and the thermostat in the hot plate.
a. With a heat enclosure plate temperature was about ± 10° F at the setting on hot plate.
b. Without the heat enclosure plate temperature was about ± 8° F at same setting on hot plate.
7. We're heating the mould with the plate temperature, NOT the air temperature, and the little difference in swing temperatures just isn't worth the bother of enclosures or PID control.
I learned a bit, had fun doing it, and again proved someone else knew a lot more than I did. I'll just write down some reference points and keep an eye on if things are in the ballpark with a hot plate and a flat aluminum cover on it.
l. Stem dial thermometers react slowly immersed in lead. They're even slower just exposed to air.
2. Even 1/8" TC probes react pretty slowly in air.
3. Realistically with a PID controlling either the contact screw-in TC and the 1/8" probe in the air could control the hot plate temperature within ± 2-3° F.
4. With the air sensor you had a constant off/on surges of power to the hot plate.
5. The mounted TC didn't ever do that for me.
6. Using the mounted TC and the Mypin just as a thermometer, and the thermostat in the hot plate.
a. With a heat enclosure plate temperature was about ± 10° F at the setting on hot plate.
b. Without the heat enclosure plate temperature was about ± 8° F at same setting on hot plate.
7. We're heating the mould with the plate temperature, NOT the air temperature, and the little difference in swing temperatures just isn't worth the bother of enclosures or PID control.
I learned a bit, had fun doing it, and again proved someone else knew a lot more than I did. I'll just write down some reference points and keep an eye on if things are in the ballpark with a hot plate and a flat aluminum cover on it.