Thermometer calibration

[NGEddie]

I boughta Brinkmann grill that I'm hoping to use for smoking and it came with 2 thermometers built into the hood. Reading online someone suggested the thermometers are often inacurate and should be calibrated, so I followed the instructions to boil a pan of water and dip the ends of the thermometer in.
I found they were only actually reading 70c when being boiled so I adjusted them up by 30c.

Sound in theory, but now when at room tempurature they read ~45c, so something's obviously wrong... was I not boiling the water suficiently hot enough?

The thermometers may just be rubbish of course, but ther are built into the bbq and I want to keep them so need to make them as useful as possible...

[keith157]

If the water is at a rolling boil at sea-level, unlike the picture, (surface covered in bubbles and occasionally spitting globules of water out) or thereabouts it will be at the right temp (100C or 212F).* Unless you are way above sea-level I would think the water would be boiling if it looks to be boiling, if that makes sense. From my VERY limited knowledge of thermometers if you adjust them up or down at the higher temps the lower temps will also change by that amount. A bit like the tare function on a weighing scale. I must point out my experience is limited and I'm more than willing to be shot down over the comment on adjustments :oops

[NGEddie]

The water did indeed bubble away nicely after I took the picture.

[keith157]

That's because you stopped watching it ...."A watched pot etc "