On 01/04/2014 06:21 PM, Shaun wrote:


"Phil Allison" wrote in message ...


"Leif Neland"
Phil Allison
Same idea as using a glass of water and a thermometer test the power
RF power of a microwave oven.

Just don't leave the thermometer in the microwave oven with the power on.

** Should be OK with a glass tube and red liquid type.


Measure the temperature of the cold water, then measure the time for
it to boil.

** Bad idea.

Takes far too long, when boiling first begins is not clear and lots of
heat
is lost to the air and evaporation.


I measured the power of my previous oven to 230W...

** Using half a litre in a plastic jug for two minutes, I got the
answer to
within 10% with a 700W rated oven.

Having a K-type bead thermocouple and digital temp meter made the job
easier
too.

You don't run it till boiling! once you get close to boiling point a
lot of extra energy is required to raise it further and make it boil.
What you do is run a glass of cold distilled water measured (temp and
volume) in a container, you could use several stacked Styrofoam cups for
insulation and cover the top with Styrofoam so that the heat generated
does not escape and run the oven till the temperature increase 20 to 50
degrees or so, then measure the temp, the information will have an
equation to convert degrees rise to microwave power. Google the method
- I haven't looked it up lately.

Shaun



.... Phil

That is not how a calorimeter works. The load must be enclosed in liquid
and must perfectly match the RF output so it absorbs all the energy.
Then the temperature should be a very accurate way to measure power. It
must be a closed, water cooled load.

http://electro-impulse.com/techinfo/calorimeters.htm