Is there a DIY method for calibrating thermometers in the 200 to 250 degree Celsius range?
In a moment of boredom I decided to put all five of my wife's oven thermometers side-by-side in the oven and set it to maximum. After waiting for them all to stabilize they all disagreed with each other over a 70 degree (C) range of values.
How can I know which one is right? (or even just 'least wrong'?)
I know I can calibrate the zero value against melting ice, and can calibrate 100 degrees against boiling water, but non of my thermometers actually go this low, and even if they did, the temperature range I'm interested in is 200 - 250 degrees.
UPDATE - I'd prefer to do this without spending too much money, hopefully no more than any of the thermometers cost in the first place. I'm looking for a solution with prove-able results. Simply buying another oven thermometer, even a top-rated one begets the question 'how do I know the new one is any more accurate?'
Incidentally, I googled various oven thermometers reviews, and non of the comparisons even mentioned accuracy, they were more concerned with ease of use and the size of the dial rather than whether or not they worked properly!
UPDATE - apparently sugar melts at 184-186 degrees - pretty close the sort of temperatures I'm interested in. This has some advantages a) I already have sugar! and b) unlike solder, I'm not going to worry about it being potentially toxic and contaminating the oven.