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TC-08 USB temperature readings fluctuate

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Re: TC-08 USB temperature readings fluctuate

Postby GiladO » Mon Jan 11, 2010 2:30 pm

I'll check it later this week.
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Re: TC-08 USB temperature readings fluctuate

Postby SJKebab » Wed Mar 31, 2010 11:04 pm

[quote="Roachtech"]I am also having this problem of incorrect readings with the TC-08 while testing electric kilns near 2000F. The readings return to normal when the electric elements cycle off, but return when the kiln controller activates the element relays. Using 7 inputs, 6 are isolated by ceramic insulators and 1 is contacting metal. Removing the thermocouple from contacting the metal does not effect the other 6 readings, nor does unplugging the laptop charger. Only temporarily shutting off the heating element power supply corrects the fluctuation problem. I'll try adding additional earth grounds to the kiln and laptop.[/quote]

One thing you must remember about a thermocouple is that it's effectively an antenna. Your heating elements will induce quite a ripple in the thermocouple output. The way I get out of these situations is to use shielded thermocouples, and then ground the shields to earth. I haven't used a tc-08 in these conditions yet, however I presume that the computer chassis will suffice as an earth here. If this isn't the case, then it might be an idea to attach a proper ground point to the tc-08 in future revisions.

This shielding technique works wonders on other data acquisition units I have here. Food for thought.
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Re: TC-08 USB temperature readings fluctuate

Postby GiladO » Mon Apr 05, 2010 4:17 pm

Not in all situations can you shield the thermocouples. In my case I am measuring temperature gradients within an oxide melt. Adding a shield is very expensive (It has to be platinum) and conducts heat which can and will effect both measurements and heat transfer within the melt.
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