Digital thermometer (with a mind of its own)

[Ray Mason]

Hi guys, I have two glass thermometers but due to failing eyesight (isn’t ageing a bitch) I decided to try a digital one from Forrtex, just a very basic model which I added to my order for an ATC800. In the mash the two glass one’s showed 66c as expected but the digital one with its NTC sensor showed 59c. The probe was at the same place, depth etc as the glass ones and so I tried the three measuring devices in a glass of water and weirdly they all showed the same temperature, ½ degree difference. Back into the mash and the difference was as before, about 6c between the glass ones and the digital. Is that bizarre or what. Any explanations very gratefully accepted. Ray.

[spook100]

Hi Ray
I can't offer you an explaination, but I have a digital thermometer that sometimes gives so weird readings. There is no way to calibrate it through the user interface but I have found that if I put the probe into an oven that has been heated up to a temperature higher than the maximum temperature of the thermometer it seems to perform so sort of 'reset to default' and all is fixed. It's probably just the way my particular thermometer works but it's worth a try.
Bruce

[Ray Mason]

Thanks Bruce, i'll give that a try. Ray

[Naich]

If there is a big lump of metal on the end of the digital one, it could be drawing more heat from the mash (causing a cold spot where it is placed) than the glass one. I find that even with a thin probe I have to wiggle it around about 3 times before the reading settles down. When you tried it in the water, there was probably enough flow round the sensor to avoid this effect.