Hello All: I discovered the lookup sheets for voltage output of a type K T/C wire and I would like to use that data on my palm pilot or computer so I could have a digital pyrometer with tracking and print capabilities. Unfortunately I am too ignorant to program so I was wondering if anyone has come up with a program to do these tasks or knew of some public domain stuff like that? Thanks, Bri.
In article , Bri writes
Unless your computer has an analogue port (bring back the BBC Model B!), you might need an A-D converter. Many such chips are available, but may require a higher input than the thermocouple will produce, in which case an op-amp pre-amplifier would also be needed.
I recently made a similar non-computerised device for raku, using a Type N thermocouple, an OP177 op-amp, and a 7107 digital display driver. This was cheating, because the output of the couple is of course not linear with temperature. However, I couldn't be bothered to use a look-up table to give an accurate reading; the Type N isn't *too* non-linear, and who cares with raku anyway?
Sorry I can't help with a computer program; I've forgotten all the Turbo Pascal I ever knew.
Regards
Jake Loddington, POULTON-LE-FYLDE, Lancs. UK
Another approach is to just buy a cheap digital voltmeter for $10 or less (Harbor Freight, etc) , and commit it to pyrometer use. You read mV directly, not temperature, but this in itself isn't much of a problem.. Usually you will be shooting for some particular temperature, which you look up ahead of time to find its mV. Then during your run you can see how close you are to the target mV... no need to know the actual temperature most of the time.
One caveat, which applies to this and all pyrometers, is that the junction of the thermocouple wires at the meter (the "cold junction" makes another thermocouple which subtracts from the main one (the "Hot junction"). So you really need "cold junction compensation", or you need another temperature measurement device to read the cold junction so you can correct your results. I think many pyrometers ignore this error, but it's definitely not negligible; just look at how close the different cone maturity temperatures are on an Orton chart.
Cold junction compensation can be done with a separate circuit that reads a thermistor, a diode junction, or a special temperature sensor chip. Or you can do it the old-fashioned way, which is to put the cold junction in an ice-water bath. That's the standard for those thermocouple charts anyway.
Bob Masta dqatechATdaqartaDOTcom D A Q A R T A Data AcQuisition And Real-Time Analysis Shareware from Interstellar Research
Oh.. this is doing it the "hard way"....
try:
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