58452 VXIbus Universal Power Meter
4-10 Publication 21555, Rev. E, September 2002
4.4.2 Power Sensor Linearity
This procedure tests the power sensor linearity over the range +20dBm to -60dBm. At low power
levels, the linearity measurement will include the uncertainty due to the zero set specification. The
procedure should be repeated for each sensor used with the power meter.
The instrument plus power sensor linearity test is valid when the sensor has been calibrated using the
front panel calibrator at a temperature between 0 °C and +50 °C (+32 °F to +122 °F), and if operating
within
± 5 °C (±9 °F) of that calibration temperature.
When measuring the linearity of a Low VSWR (Series 8031XA) or a High Power (Series 8032XA)
sensor, the power output of the source must be increased from 10dB to either 16 or 20dB respectively
(See Figure4-3). The power coefficient of the step attenuator will also have to be considered. The
specification of power coefficient for the Weinschel attenuator cited in the Equipment List is:
<0.005dB/dB/W. The latter will effect the linearity of each 10dB segment, and make it necessary to
expand the overall linearity specification by this quantity.
Connect the test setup shown in Figure 4-3. In assembling the test setup, keep in mind that if testing is
to be conducted with Low VSWR or High Power sensors, the optional RF Amplifier must have
frequency and bandwidth to match the sensor’s characteristics (See the Sensor Selection Guide in
AppendixB), and the Directional Coupler must be increased as stated above for the particular series of
sensors. All Standard (Series 8030XA) and True RMS (Series 8033XA) sensors are tested without the
optional RF Amplifier, and with a 10dB Directional Coupler.
Refer to the Linearity Data section of the Performance Verification Test Data Sheet at the end of this
chapter. The tolerance is already entered for the various steps and includes an allowance for specified
zero-set errors at low power levels.
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