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Resistor: Low Heat Capacity, Low TCR, Constant heat dissipation

by marklv87
Tags: capacity, heat, resistor, tcr, wattage
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Dec20-09, 01:44 PM
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I am looking for a resistor that can dissipate a constant amount of heat at all temperatures immediately.

I have been using some metal film/oxide resistors, but it takes a very long time before the resistor starts radiating heat. I think the material making up the resistor has such a high heat capacity that it takes a very long time for it to completely heat up the material before it starts radiating the ambient air (especially at very low wattage like 1/2W).

Could anyone tell me what the best type of resistor to use for quickly generating a constant amount of heat, but also keeping a constant resistance (low TCR)?
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Dec20-09, 08:45 PM
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The time something takes to heat up depends on its mass and specific heat and temperature differences or the power supplied if it is resistive heating.
Very small resistors with enough power going into them to behave like this would be destroyed in seconds.

If you just want infra red radiation, maybe you could look at infra red diodes?
Dec21-09, 01:04 PM
P: 2
Thanks. I actually a constant heat source for the calibration of a calorimeter. Do you have any ideas for something that produces a constant amount of heat and has a known wattage, besides a resistor?

Dec21-09, 01:46 PM
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sophiecentaur's Avatar
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Resistor: Low Heat Capacity, Low TCR, Constant heat dissipation

What about a hefty lamp filament? They can get V hot without frazzling and can handle lots of watts. You'd have to control the voltage to give the appropriate temperature / resistance but that goes for any resistor over such a temperature range.

Why does the warm-up time bother you? You can always use a shutter to keep it away from the experiment until it's hot enough.

The surface temperature will be a function of power and surface area. I think you need to specify what you actually want in terms of the spectrum of the radiation before you can make a proper choice of resistor type and its value.
Dec21-09, 05:22 PM
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Kaye Instruments make calibration and validation equipment which I've used in the pharmaceutical industry. Here is a sweet dry-well temperature block. And if you want a good temperature standard to go along with it, I would recommend this Intellegent Resistive Thermal Device which is good for 0.025C.

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