Giga-tronics 8650A Series, Operation Manual

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Series 8650A Universal Power Meters
4-6 Manual 31470, Rev. E, April 2001
4.4.2 Instrument Plus Power Sensor Linearity
Test Description
Connect the test setup as shown in Figure 4-2. The linearity will be tested over the range +20 dBm to
-60 dBm. 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 8650A.
When measuring the linearity of a high power sensor, the power output of the source as well as the
directional coupler coupling factor, must be increased. 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: <0.005 dB/dB/W. The latter will affect the linearity of each 10 dB segment, and
make it necessary to expand the overall linearity specification by this quantity.
In assembling the test setup shown in Figure 4-2, 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
parameters to match the sensor’s characteristics (see the Sensor Selection Guide in Chapter 1, if unsure
of characteristics), and the Directional Coupler must be increased as stated above for the particular
series of sensors. All Standard (Series 8030X) and True RMS (Series 8033X) sensors are tested with a
10 dB Directional Coupler and without the optional RF amplifier.
Refer to the Linearity Data recording section of the Performance Verification Data recording sheets
located on pages 4-9 and 4-10. The tolerance is already entered for the various steps, and includes an
allowance for specified zero set errors at low power levels.
Figure 4-2: Power Linearity Test Setup
NOTE:
To ensure accurate and repeatable measurements, the 432A power meter should be
zeroed just before taking each reading that will be used to calculate P1 in the Power Meter
column of the Performance Verification Test Data Sheets on pages 4-9 and 4-10.
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