Questions on thermometer calibration?

[qdog1955]

  Decided I should check and calibrate my 12 inch thermometer. Here's what I did-----should I have done something different?
Using the packed ice and water method, I first calibrated my digital thermometer ( manufacturers recommended method ) to verify any readings. When  I placed the 12" in the 32 degree water I'm reading 40 degrees----when placed in boiling water I get 209 degrees---high at one end, low at the other. To keep the story short---after making numerous adjustments and checks it was always high and low to various degrees, but seemed less so in the middle heat ranges-----so I calibrated at 100 degrees as this is probably the closest to the range I use most often. How do you guys and gals calibrate?
  This thermo. was probably intended for brewing and up until now has always been within plus or minus 2 degrees.
Any tips or suggestions?
Qdog

[awakephd]

Not too long ago I read an excellent suggestion here on the forum; unfortunately I can't remember who made it.

Use a glass thermometer for measuring human temperature; it will give very accurate results right in the sweet spot of the target range, 98.6˚! Just be careful not to subject it to anything hotter than about 105˚, lest it burst ...

[scasnerkay]

I have checked for accuracy the same way - ice with a little water, and boiling water. I have some thermometers that are able to be calibrated and some that are not. I usually use more than one thermometer during any make just to cross check. I have thrown out some thermometers that were off.

[OzzieCheese]

I normally use thermometers from Green Living Australia,
http://www.greenlivingaustralia.com.au/cheeseaccessories_thermometers.html#cheese_thermometers
they are a reasonably generic one with a locking(adjustment) nut on the back.
I use the the Ice method to set one thermometer (-A) to the low end and boiling water for another to the high end (-B).  Unless you are at a wierd elevation water, I'm only 22 feet above Sea level, water boils at 100 Deg C.  Now if you really want to get fancy.  Get the one you have adjusted to 100 (B) - because it's an accurate point - turn off the kettle or whatever you are using and let the water cool. These dials are symetrical and therefore at 52 deg C is the centre reading. The funny thing is that because the needle movement is a linear representation of expansion, now you can divide the high and low variance. So put (-A) in and calibrate it to 52 deg when (-B) reaches 52 deg.  Its a bit of a long process but if you now check the newly calibrated (-A) at Ice and Boil it should be very close.
Or you can just get a precalibrated digital one and hope it's correct - me.. I still trust the physical over the digital, and yes I like to read real books as well ...

-- Mal

[qdog1955]

Hey PHD---said I'd try to keep it short----but did use two other thermos.----a mercury, used in chemistry, and one used in developing film---those were spot on.
  Susan----I think this one may go to the landfill.

And Ozzie----it's getting scary---I'm thinking like an Aussie ---that's pretty much what I did----I have 5 hours of checks and notes. I'm old school ,too---except I got away from that primitive metric stuff ------and my kindle has been replaced with modern paper style books.

[John@PC]

I swear I posted a reply on this but must have not hit the send button .  At risk of duplicating depending on type of analog thermometer it could have some mechanical hysterisis which would explain higher than lows and lower than high readings.  The comment about using an oral thermometer is spot on - best way to make sure you're reading correctly near that 100F range.

[OzzieCheese]

@John, I didn't want to get too technical but yes physical hysterisis is an issue...
@Q  - Primitive Metric !! Sorry Mate, I grew up on Gallons, pints Pound and Ounces - Pity a US Gallon/Quart/Pint/Long Tons/Short tons is different from an imperial Gallon/quart and Pint - And then sanity gave us Tonnes/Grams/litres/Mls and degrees Celsius.  I'd rather mulitply and divide by 10's any day.
   
Just sayin

--Mal

[qdog1955]

John ---Mal----had to look that one up, 'cause I was pretty sure you weren't implying my thermometer was being a comedian
Mal hope you took that as a joke, the way it was intended-----grew up with all that stuff, too---but in the USA we have added metric and still kept all the old stuff, to make it even more confusing----and that's why I consider it a big joke here----come on USA---one way or the other!!

  Have been making a lot of Alpine style cheese lately and of course the temps are higher and became concerned on under and overshoot ----the question now, even if I replace the thermometer is the hysteresis going to be a continuing concern?
Qdog

[OzzieCheese]

Yo Q !! Of course I feel your pain. Now if we could convert to a Decimal Time how sweet would that be 1 tick - (pick another atom state to measure), 10 ticks to a tickle, 10 tickles to a tockle, 10 tockles to a 1 trickle and as all my days start trickling away, all of a sudden i'm in the looney bin trying to differenciate between my tics from my tocks.  Oh... off topic again, sorry. 

-- Mal 

     

[Stinky]

During the French revolution, for some time they implemented a decimal clock. 

[qdog1955]

I an attempt to avoid a time, temp. continuum----I'm staying away from both of those
Qdog