On 5/4/2015 2:53 AM, Bill Turner wrote:
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On Mon, 04 May 2015 02:24:56 -0400, K8RI wrote:
Measuring the temperature rise in a known quantity of water with a known
heat loss is limited by the system's heat loss. Water is straight
forward as an instrument as 1 calorie will raise the temperature of 1cc
or gram of water 1 deg C. (I'd have to look up the number of joules
required) You can graph the heat rise vs time, and or reach
equilibrium at a given heat loss (the temp of a given volume of cooling
water at a given rate. Then you are limited by how accurately you can
measure the flow and temp.
REPLY:
That method will work but for our purposes it's probably overkill.
Absolutely.
Way overkill and too much work for what you get.
An
easier and quicker way is to measure the hear rise with the unknown RF
and again with known DC or low frequency AC. When you get the heat
rise the same, you have your answer.
Technique is important, mainly in keeping the environmental conditions
the same between tests. Same room temp, same room air circulation,
etc. You don't even need a particularly accurate thermometer, just as
long as it is repeatable, which most are.
IOW eliminate all the variable that are not necessary and identify the
unknowns.
Settle for repeatability where absolutes are not relevant. Don't
measure to 3 decimal places when one significant digit is sufficient.
"Simplify"! As in math substitutions may work better and be easier to
obtain than measuring the specific unknown.
73
Roger (K8RI)
73, Bill W6WRT
73, Bill W6WRT
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