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Malintent · 03-04-2011, 03:56 PM

I know how to calibrate.. not a problem. My concern is the amount of offset. 13+ degrees seems excessive. It reads higher than actual (it needs a -13 offset). It is a pt100 RTD on a cheap Auber PID (both bought from Auberins). I cut the very ends of the probe wire off to remove the terminal connectors, then soldered it to a 3 prong socket (also from Auber).

My question is, should I be concerned that this is indicative of a poor solder joint (higher resistance = higher indicated temp), a bad probe, or is an initial 13 degree error on par for what you guys have seen with these?

**Walker** · 03-04-2011, 05:20 PM

Quote:

Originally Posted by Malintent

I know how to calibrate.. not a problem. My concern is the amount of offset. 13+ degrees seems excessive. It reads higher than actual (it needs a -13 offset). It is a pt100 RTD on a cheap Auber PID (both bought from Auberins). I cut the very ends of the probe wire off to remove the terminal connectors, then soldered it to a 3 prong socket (also from Auber).

My question is, should I be concerned that this is indicative of a poor solder joint (higher resistance = higher indicated temp), a bad probe, or is an initial 13 degree error on par for what you guys have seen with these?

No.. that seems bad. My cheap chinese RTD has an error of 1.5*F. My even cheaper chinesier probe that ended breaking on me had an error of 3.1*F.

I would think that one from Auber should be pretty damn close to correct.

Did you test the probe with the PID before you cut and soldered through the connector?

The soldering shouldn't be causing you a problem unless your work was really crappy one wire and not the others. The whole point of the RTD's having three wires is to compensate for the resistance in any leads and connectors on the path between the probe and the device using the probe.

If you didn't check it at first with probe directly connected to PID, it might be worth the effort to unsolder the thing and test it directly connected.

13*F seems too much of an error to me, but I AM NOT AN EXPERT.

Malintent · 03-04-2011, 07:05 PM

I just got off the phone with their tech support. they agree that 13 degrees F is excessive. they also confirmed the 3 lead wire redundancy makes a bad solder joint unlikely (both red leads would have to be nearly equally bad).

there are four possibilities

1) air trapped in the tube by the probe
If the probe is not completely submersed, a HIGH reading is possible (this I didn't quite understand - I would have thought it would be low)

2) My reference thermometer is bad (not likely)

3) I have two bad solder joints. I was told to measure the resistance in Ohms between matching pins on either side of the wire assembly (each 1 Ohm of resistance in both red wires would lead to 1 degree C of error, high.

4) I was sent a faulty probe.

If I eliminate 1 - 3 as the culprit, they offered to exchange the probe out, even though I modified it (with the connector bought from them).

Any other opinions or comments are still very welcome!

**Walker** · 03-04-2011, 07:25 PM

1) air trapped in WHAT tube? is this in a RIMS pipe? If so, you can eliminate #1 and just unscrewing the thing and see if it's still off by 13*F.

2) boil water and check it with your reference thermometer and the rtd from auber. should be 212*F.

3) this could also be checked by unsoldering and checking with the probe directly connected to the PID.

Malintent · 03-04-2011, 10:55 PM

32.0 F on the dot.

I did an ice water check and my refrence thermometer seems to have been damaged recently (my gear has been in storage for the winter). It read around 22 or so in the ice bath.

Yes, Walker, this is a rims pipe... a new project to kick off the season