Power Linearity Test Setup; Figure 5-1 Power Linearity Test Setup - Giga-tronics 8502A Operation & Maintenance Manual

Series 8500A Peak Power Meters

5.2.5 Power Linearity Test Setup

To make accurate measurements using the thermistor power meter, it is essential that it be zeroed
properly. This should be checked frequently, keeping in mind that the instrument must be zeroed again if
any drift has occurred.
For each value of attenuation the following steps are to be performed:
1. After initial power-on and warm up, set the PPM to read CW power in milliwatts, with the CW
averaging number set to 500. This is done by pressing [CW] [MENU] (2) [F1] [500] [UNITS]
2. Check that the display indication is in milliwatts. If not, press [MENU] (4) [F3].
3. Be sure that the RF source is set to 1.0 GHz.
4. Perform an automatic calibration on the detector (use channel A for an 8502A). Use this detector
for the rest of the test.
5. Automatic calibration is performed by first attaching the detector to the 1 GHz Calibrator
connection on the front panel of the PPM, and then pressing [MENU] (1) [F3] [F1] [UNITS]
6. Be sure that the Thermistor Power Meter is zeroed correctly. Adjust the RF source for a reading
of 10.0 mW ±0.25 mW.
7. Record the Power Meter Reading and the PPM Reading in the corresponding columns of the CW
Linearity Data section of the Performance Verification Test Data recording sheet.
Adjust the source to read 1.0 mW ±0.025 mW.
8.
9. Record the Power Meter Reading and the PPM Reading in the corresponding columns of the Test
Data recording sheet.
10. Calculate the power ratio and reading ratio (using P1/P2 and R1/R2), and record these values in
the indicated columns of the Test Data recording sheet.
11. Calculate the linearity error using the formula:
Linearity error (%) = [(R1/R2) / (P1/P2) - 1] * 100
5-4
Figure 5-1. Power Linearity Test Setup
Manual No. 20790, Rev C, November 1998