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Calibrating for Increased Measurement Accuracy
Power Meter Measurement Calibration
Power Meter Measurement Calibration
A GPIB-compatible power meter can monitor and correct RF source power to achieve
leveled power at the test port. During a power meter calibration, the power meter samples
the power at each measurement point across the frequency band of interest. The analyzer
then constructs a correction data table to correct the power output of the internal source.
The correction table may be saved in an instrument state register with the SAVE key.
The correction table may be updated on each sweep (in a leveling application) or du ring an
initial single sweep. In the sample-and-sweep mode the power meter is not needed for
subsequent sweeps. The correction table may be read or modified through GPIB.
Power meter calibration is useful for the following applications:
• when you are testing a system with significant frequency response errors (for example,
a coupler with significant roll-off, or a long cable with a significant amount of loss)
• when you are measuring devices that are very sensitive to actual input power for proper
operation
• when you require a reference for receiver power calibration
The power meter can measure and correct power in two ways:
• continuous correction—each sweep mode
• sample-and-sweep correction—single sweep mode
The time required to perform a power meter calibration depends on the source power,
number of points tested, and number of readings taken. Refer to the “Specifications and
Characteristics” chapter of the reference guide for characteristic power meter calibration
sweep speeds and accuracy.
Regardless of the measurement application, the analyzer's source can only supply
corrected power within the selected power range. If power outside this range is requested,
the annotation will change to PC?.

Loss of Power Meter Calibration Data

The power meter calibration data will be lost by committing any of the following actions:
Turning power off. Turning off the instrument erases the power meter calibration
table.
Changing sweep type. If the sweep type is changed (linear, log, list, CW, power) while
power meter calibration is on, the calibration data will be lost. However, calibration
data is retained if you change the sweep type while power meter calibration is off.
Changing frequency. Power meter calibration data will also be lost if the frequenc y is
changed in log or list mode, but it is retained in linear sweep mode.
Pressing . Presetting the instrument will erase power meter calibration data.
If the instrument state has been saved in a register using the key, you may
recall the instrument state and the data will be restored. Saving the instrument state
will not protect the data if the instrument is turned off.
Preset
Save/Recall