A little over a year ago I purchased an expensive digital scale / thermometer combo: http://www.breville.com.au/thelittlegeniustm-kitchen-scale.html
It works fine however recently I took a go at testing the thermometer to see if it was reading accurately. I fill a pan up with water and left the probe sitting in, waiting for the water to boil.
When the water was a rolling boil, the thermometer was only reading about 94C or 96C (can't remember which one, will do another test tonight), which was disappointing given the cost of the product.
The scale has a five year replacement warranty so I sent an email through to the customer support department. This was their response:
Thanks for your enquiry.
The temperature probe tolerance is +/- 5 percent and there is no way of resolving this.
Hope this helps with your enquiry.
Personally, I find this hard to believe and couldn't see it specified anywhere on their website. The thermometer is stated to work up to temperatures of 150C, which, means it could vary as much as 7.5C at that level...
Given that the thermometer gives reading to one decimal point (i.e. 96.6%) it seems ridiculous to accept that the temperature could actually be anywhere between 91.X% to 100.X%.
Is this to be expected with food thermometers or should I argue my case? Are there any other reliable thermometers I can use as a point of reference?
EDIT: Did some further testing over the weekend. I tested it again in a shallow pot of boiling water and it was hovering around the 96C mark. After filling the pot so that most of the probe would be submerged, it began to hover between 97C and 97.5C.
I also tested it in a cup full of ice cubes and it read 0.0C...