My entry into this Inexpensive Temp Probe Derby is based on a thin film platinum device from, you guessed it, Digikey. Suprisingly, they are cheap, accurate, but also very tiny.
I thought some of you might be interested in another way to git'r done.
What I have now is basically a GTP 59 probe clone.
I bought a bunch of TE pn 223-1820's which are 1kohm units. To get the required 500 ohms for the GAD 13, I put 2 in parallel to make what is effectively a single 500 ohm device. One connection goes to GAD13 pin 6. The other side of the device goes to pin 3 AND 8 with a jumper.
If you are all about precision( i am), or have a long run or are using thin wire, consider using 3 wires. In this case, run 2 separate wires from one side of the device to pins 3 and 8 of the GAD 13 - no jumper. This is the way the GTP 59 is installed. It only makes a very small difference. Spruce's 24 gauge x 3 shielded cable or similar might be a good choice for probe cable.
Tested accuracy was pretty good. Distilled water ice temp was spot on 32F. Boiling water temp was ~207.9F. The calculated temp for my pressure altitude was 209.33F. So, off by ~1.5F, quite good. Less than 1 degree C. This will correspond to a small fraction of a degree at flight air temps. Testing was done using 2 short wires and jumper.
ron
Last edited by Cumulo : 10-19-2019 at 01:50 PM.
Reason: expanded
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