Digital Thermometer Differences Uh-Oh??

[doberman]

I just purchased a larger, easier (much) to see LIFEGUARD digital thermometer - have been using the smaller version by the same company - I have the probes right next to each other about 2/3rds of the way down in a 25 gallon tank - the small one reads 77.4 and the big one 79.4 a difference of 2 degrees!! Which one should I believe and how would I calibrate them (probably not possible) - what then would/should I use to VERIFY which one is more/most accurate??

[wharyat]

I have a laboratory grade (30cm long, extremely accurate) mercury thermometer that I use. I have found no digital that is even within one degree of it.

[Phishnoob]

I would get a cheapo mercury thermometer and calibrate a thermometer against it. There should not be a lot of slope over a very narrow range of temps so a single point cal should be enough to stay within a degree.

My buddies wife can come over and stick her elbow in the water (works for bath water) if that doesn't work.

[VWD]

some of the old mercury are thet best way to go. digital is hit or miss when You get just the average or low end stuff.

[Loverotties]

put the probe in a glass packed with ice and add a little water to wet the probe and it should give you 32 deg reading.

[wharyat]

Great suggestion rotties!