Thread: The Heat Die
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Unread 09-02-2003, 09:52 AM   #6
bigben2k
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Join Date: May 2002
Location: Texas, U.S.A.
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Actually, I was refering to Joe Kelly's bench, not Joe Citarella, but that's a good link, thanks!


joemac: I understand, from correspondence with your partner, that you've been looking at TECs because of this issue that resistor's actual values can shift over time and use. My reply to that (someone correct me if I'm wrong) is that it's really irrelevant, because regardless of the actual resistance, the power is measured by the voltage, and amperage.

So I'd refer you to RoboTech's heaters (if I had a link). They're that small cylinder that you know about. They can be mounted inside of a copper or brass die, and then insulated, to minimize the secondary heat losses (a source of error, at ~2%). A power resistor may work, but it may be a bit less convenient to deal with, I think. Dan From dansdata.com uses one.

As for TECs, I don't know how reliable that would be, as a heat source: Since it "moves" heat, using the power that is provided to it, the end result may be somewhat unpredictable. You also have to consider the clamping pressure, which could then become another variable, and source of error. We want to minimize the errors, as much as possible, because we can barely afford it.

So a heater/resistor is easier to deal with, because the power measurement is direct, and the accuracy is simply down to that of the meters.

One thing I've been pondering on and off for some time, is if it's possible to use the same meter, and switch back and forth, between measuring amps and volts. Then it occured to me that the amp measurement, if it's a tap in the power line really can't be interrupted, but there's always the amp probe, or alternatively, if it's acceptable, a power shunt, which has its own set of variables... But that's a discussion for this thread.
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