REFLECTOR: Thermocouple Calibration

[Scott Derrick]

My soldering station   
http://www.circuitspecialists.com/prod.itml/icOid/7508

has a calibrated temperature setting up to  900F.   You couldn't do up 
to 1500F which would be ideal but 900F pretty good.

know a hardware geek with one?  Actually Brian I would be surprised if 
you didn't have one?  Is this what you where going to heat a solder pot 
with or do you have a calibrated  solder pot already?

Scott

Brian Michalk wrote:
> This weekend I had the second engine start, and the goal was to dial in 
> the electronic fuel injection system.  I was going to do that using 
> EGTs.  I had picked four sites on the fuel table and was going to run up 
> to peak EGT, then go to 25 rich of peak.
>
> Well, Murphy said it wasn't going to work.  My panel gauges didn't work, 
> and my engine monitoring EGT thermocouples didn't work either.  A long 
> time ago I decided to terminate the thermocouples in the cabin, thus 
> locating the cold junctions in the cabin which is a more stable 
> temperature environment.  The gauges are calibrated by Westach for 75F. 
>     When I did this, I had to add thermocouple wire to my probes, and in 
> doing so made probes that had more resistance than what the gauge was 
> calibrated for.  I trimmed them for the same resistance, and just forgot 
> that I needed to send the gauge back for a recalibration.
> The reason the electronic EGT probes didn't work is because my CPU runs 
> on 3.3 volts, and the A/D converter on the CPU can only sample up to 
> it's VCC (3.3V).  The AD595 I was using outputs a signal of 10mV/C, so 
> above 330C, the A/D sampler is saturated.  So for the sake of dialing in 
> my engine, both systems were inop.
>
> I have now added a gain resistor to the AD595 to move it from 10mV/C to 
> a more manageable 1mV/C.  However, resistors being what they are, I want 
> to calibrate my thermocouples.  I've thought about using a solder pot 
> full of solder.  I've thought about using a hot air gun, and another 
> thermocouple as a reference.  Boiling water is okay, but I'd like to 
> calibrate to something over 500 degrees.
>
> Do any of you guys have any thoughts as to a cheap temperature reference 
> I could use for calibration?
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