Measuremet Uncertainty Analysis - Instrument Accuracy Test D
Keysight E4416A/E4417A Power Meters Service Guide 163
Uncertainties
* 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
offset 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
example, 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).
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
*
Extraneous signals, cables connectors and Yes (Type A)
Test Station Error (TSE) is the error contribution of the cables, connectors, noise,
and so forth, that cannot be measured independently.
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