"bill" > wrote in message ...

> Just how is an oven thermometer tested for accuracy and
> repeatability and if it's off how is it calibrated ?

A glass thermometer with a mercury column can be a fine
temperature standard provided it is properly calibrated by
its manufacturer.

Such could be used from time to time to check the accuracy
of an ordinary (bimetallic) oven thermometer, which is a
more practical device inasmuch as a glass thermometer is
hard to read through an oven door.

A more elegant solution for studying oven temperature is a
thermocouple thermometer calibrated at two points, like
melting ice in distilled water at known atmospheric pressure,
and melting pure metal, like bismuth or tin. Of course, you
would probably want also to use a data-logging device if
you went that far.

For most people, the most practical solution would be to note
the thermostat setting that does the job best, and use that setting.
Not to worry until a poor result is got.

--
Dicky