Ha, thought the same thing, then wondered if there was just a slight cooling effect in action (low ambient temps, going through the tube with the laser not in use).
Looking at your pic/comment again I can see it’s a home made sensor. I assume you’ve tested the for variances considering it’s not in direct contact with the water?
Yuusuf;
The temp gauges are real inexpensive and not super accurate. I powered all 5 of them up and at the same time and let them sit for 30 minutes to stabilize. They all read different, but were close +/- .5c - 1.5c. I just picked the two that were closest.
@Todd_Miller Haha. I see; that explains how it gets colder as it passes through the laser tube. Thanks for explaining that one. At least you know the temperature roughly (within +/- 2c). For the purpose, I think we don’t need much more precision than that.