Figure 4. Power reference level

Calibration Procedure For Power Meter, Model 438A And 438Aopt002 Page Navigation
12

TB 9-6625-2278-24

Figure 4. Power reference level - equipment setup.

(7) Set power meter power pushbutton to ON position.

(8) Set TI LINE switch to ON position and POWER REF OSC switch to off (LED off).

NOTE

Allow equipment and thermistor mount to warm-up for 30

minutes before proceeding to (9) below.

(9) Set power meter RANGE switch to COURSE ZERO and adjust front panel

COURSE ZERO control for a zero meter indication.

(10) Fine zero power meter on most sensitive range then set power meter RANGE

switch to 1 mW.

(11) Ensure multimeter input terminals are isolated from chassis ground for

(12) below.

(12) Adjust multimeter to measure microvolts dc.

(13) Connect multimeter positive lead to power meter Vcomp (fig. 4) and connect

multimeter negative lead to power meter VRF (fig. 4).

(14) If multimeter indication is 400 V or less, record multimeter indication and

proceed to (16) below; if not, proceed to (15) below.

(15) Hold power meter FINE ZERO CONTROL and adjust COURSE ZERO

control for a multimeter indication 200 V or less. Record multimeter indication.

(16) Round off indications recorded in (14) or (15) above to the nearest microvolts and

record this value as V0 .