MM0474
Figure 7.
Total Uncertainty After Correction.
(8) Effective Efficiency.
Effective Efficiency is the ratio of
substituted audio or DC power in the thermistor mount to the microwave RF power
dissipated within the mount.
This power ratio corrects for RF losses and DC-to-microwave substitution error
in the thermistor mount. It is largely independent of the level of input RF
power. When a tuner is used to present either a conjugate or Zo match to the
microwave RF source, Effective Efficiency is to be applied as a correction
factor to the power measurement because all of the power incident upon the
mount is absorbed in the mount.
The use of a tuner and application of
Effective Efficiency is the most accurate method of measuring power since
source and thus, measurement uncertainty due to mismatch is eliminated. Tuner
loss will generally be small.
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