Thermometer calibration.

[Easydrinker]

Something currently bugging me is not knowing which of my thermometers to believe.
I own more than two dozen, from cheap Chinese LCD's to more expensixe LCD's. some with red liquid in and some I think with Mercury, a point press/the trigger jobby, some stick ons, one for jam, one for cooked meat, one in the fridge that say's OK if it is cold enough, - you name it ,I probably own it!
I only usually ask of them to be consistent in the job that I ask them to perform, not caring if it was the actual temperature.
Last week I wanted an absolute,spot on temperature.
I finally found two thermometers to agree, but were they right?
With clocks and time, you can get the radio signal controlled ones, no probs.
Back when I sailed off the west coast, if I was near a Coast Guard station and they announced the barometric pressure, i could adjust my inferior barometer.
How do we get a low down on temps?
We can photograph black holes a gazillion miles away, but am I to believe some spotty kid that wrote an App. telling my via the internet that at my postcode it is however many degrees C?
I have buggered a couple of themometers putting them in boiling water trying to calibrate them.
But I live 225 Meters above Sea level, so that was always doomed to failure.
Another point, - do thermometers understand altitude?

I may be a little dumb here. Certainly a little drunk.
If anyone can give me a decent comeback, I would be grateful.

Robert.

The thought has just occurred, I could stab myself with one and check my body temp.at 37°C.
But what if I am running a fever, or suffering from the current cold spell outside?
This could be a whole new can of worms.

[Mash]

Altitude is the reason you don't use boiling point, unless you adjust it.

A saucepan or bowl full of ice water should stabilise at 0c after a couple of mins. Use as much ice as you can fit in.

Hows the head? Some ice with that sir?

[myles]

Thermometers may not understand altitude but water does.
http://www.csgnetwork.com/h2oboilcalc.html
It always boils at the correct temperature for the barometric pressure at that moment in time. Tables for that are available.

I always calibrate for boiling point as I tend to be more interested in the higher temperatures. If I really wanted to be sure about the lower temperatures I would calibrate with ice/water mix.

[Easydrinker]

My best guess, is that as when caliibrating most measuring tools, you aim for both ends of the spectrum, if you can?
Thanks for that link Myles, I had a quick look and will go and play tomorrow.

Robert.