Measurement Uncertainty Analysis - Instrument Accuracy Test D
E4416A/E4417A Power Meters Service Guide D-151
Uncertainties
Define the Measurand
The measurand is the Measurement Accuracy of the DUT.
Define the Measurement Equation
Measurement Accuracy = DUT Measure - Test System Power
Where:
Test System Power = (Measure voltage × Volts/Power Conversion) + Test
Station Error
Universal Source: No Uncertainties
DMM: Yes (Type B)
8482: No
*
* There is no uncertainty involved within the 8482A sensor, as a relative power is being measured.
Before any measurement is made, an equivalent voltage to 0 dBm is applied to the 8482 sensor to
allow the power meter calibration.
It is not important if the sensor creates an offset during this calibration procedure, provided this off-
set is present throughout all the different power levels. The 8482A sensor is linear from −25 dBm up
to 0 dBm, and hence the same offset would always be present. Between 0 dBm and 20 dBm, look
up tables are employed to counteract the non-linear behavior of the sensor at higher power levels.
Example: Consider a DC voltage from the Universal Source applied to the 8482A sensor, producing
a power of 0.2 dBm instead of 0 dBm (for example, a 0.2 dBm offset). The measuring device (for ex-
ample, the power meter) takes this 0.2 dBm value as being 0 dBm, and adjusts itself accordingly.
Now throughout every measurement level, the 8482A and the power meter has the same 0.2 dBm
offset (because the sensor is linear).
Extraneous signals, cables connectors and Yes (Type A)
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