Accurate PT100 Temperature Probe

[blawford]

I am looking for a screw-in PT100 that reads the correct temperature. I bought one of these https://www.ebay.co.uk/i/122478920037?rt=nc and although it seems good quality, the temperature reads +2-3c in ice water and 97c in boiling water.

Does anyone have any recommendations of other probes, or if anyone has bought the same one, was it accurate? I'm not sure whether this is just a one off or not.

 

[Dutto]

Rather than go through the trauma of buying yet another slightly inaccurate probe I would:

A) Make out a chart that shows the "Read v. Real" temperature.

or (most likely)

B) Not bother doing anything. This would be on the basis that a couple of degrees at freezing or boiling are meaningless as the only temperature sensitive elements of brewing are during Mashing and Fermenting.

Also, with identical errors at both extremes the probe MUST be accurate (*) somewhere within the range; and the chances are that it is within one degree in places where accuracy is needed.

If you want a probe with a greater calibrated accuracy, I'm afraid that you must pay a lot more that £7.99 for the pleasure!

Note:

Do you realise that a broken watch is more accurate than a watch that loses one minute per day?

Logic dictates that a broken watch will accurate TWICE per DAY whereas a watch that loses one minute per day is only accurate ONCE every 3.9 YEARS!

 

[foxbat]

The ebay probes are somewhat random in their calibration. I have several of them and high-precision conversion circuitry that I designed myself and none of them are close enough to true to trust for fermentation or mashing without calibration. The linearity of the PT100 response is close enough to flat over the range you care about that you can take Dutto's lookup-table approach or use a simple constant offset if you trust that the ebay probe actually has a platinum element at all. If it's from China you should start from a position of not trusting it.

Good RTD probes will not be cheap. Thermosense do a good range at reasonable prices (for PT100 RTD probes). You may be able to find one that works for you. RS also have a good range.

 

[BeerCat]

I have no tested mine like you but I compared it at mash Temps with an analogue and an stc with stainless probe. Was very close I have a very cheap probe which is way off and rusting!

 

[blawford]

Rather than go through the trauma of buying yet another slightly inaccurate probe I would:

A) Make out a chart that shows the "Read v. Real" temperature.

or (most likely)

B) Not bother doing anything. This would be on the basis that a couple of degrees at freezing or boiling are meaningless as the only temperature sensitive elements of brewing are during Mashing and Fermenting.

Also, with identical errors at both extremes the probe MUST be accurate (*) somewhere within the range; and the chances are that it is within one degree in places where accuracy is needed.

If you want a probe with a greater calibrated accuracy, I'm afraid that you must pay a lot more that £7.99 for the pleasure!

Note:

Do you realise that a broken watch is more accurate than a watch that loses one minute per day?

Logic dictates that a broken watch will accurate TWICE per DAY whereas a watch that loses one minute per day is only accurate ONCE every 3.9 YEARS!

Spot on Dutto. I did a test controlling water between 60c and 70c using my sous vide immersion circular. Versus my Thermopen, it was within 0.5c across the range, so good enough.

Thanks.

 

[aamcle]

Used to buy cheap Chinese Class A sensors and soldered on leads and connectors.
I found them accurate, if the were 3°C in ice water they were 3 out in boiling water, there is a setting in my PID that allowed me to fix the calibration so it read 0°C in ice water and 100 in boiling water.

I think I paid under £5 including shipping.

https://www.ebay.co.uk/itm/0-2-Clas...885727&hash=item21004cd725:g:dl8AAOSwNSxVUdXK

aamcle