TB 9-6625-2185-35
meter and pin 1 of interconnect cable.
(4) Record bridge resistance value (2 decimal place resolution) as indicated on
digital multimeter as R (approximately 200Ω).
(5) Disconnect multimeter and set to read dc V.
(6) Reconnect thermistor mount to interconnect cable and press power meter
power to ON. Allow power meter to stabilize.
(7) Connect digital multimeter to VCOMP (+) and VRF (-) jacks on rear of power
meter.
NOTE
Ensure that digital multimeter input leads are isolated from
chassis ground in following steps.
(8) Set power meter RANGE switch to COARSE ZERO and adjust front panel
COARSE ZERO control for a zero meter indication.
(9) Fine zero power meter on most sensitive range, then set power meter
RANGE switch to 1 mW. If digital multimeter indicates less than 400 mV, record this
value to the nearest microvolt as V0. If value is greater than 400 mV, rezero power
meter.
(10) Connect thermistor mount to PWR REF and record digital multimeter
indication as V1.
(11) Disconnect digital multimeter (-) input lead from the VRF connector and
reconnect to power meter chassis ground. Record digital multimeter indication as
VCOMP.
(12) Calculate PWR REF output power using the following formula:
2 V COMP (V 1 - V 0 ) + V 02 - V 12
PO =
Where:
PO = Power output in watts
V COMP = Value recorded in (11) above
V 1 = Value recorded in (10) above
V 0 = Value recorded in (9) above
R = Value recorded in (4) above
CALIBRATION FACTOR = Test report value for thermistor mount at 50 MHz (or other test frequencies
being measured).
NOTE
The technique of (7) through (12) for measuring power will be
used throughout this procedure and will be referred to as
precision power measurement technique.