Cal Power TrueWave TW1750, Service Manual

Page: 42 / 84

CALIBRATION TW SERIES
3-6
Calculate the gains and offset for the phase being calibrated:
GAIN1 = ( MEAS1 – MEAS2 ) / ( RDGN1 – RDGN2 )
GAIN2 = (440.0) / ( MEAS1 – MEAS2 )
OFFSET = GAIN2 * MEAS1 – 220.0
Update the TW calibration registers by sending the following GPIB strings:
CAL {1,2,3} :MEAS:LOC:LOR:VOLT:GAIN GAIN2
CAL {1,2,3} :OUTP:LOC:LOR:VOLT:GAIN GAIN1
CAL {1,2,3} :OUTP:LOC:LOR:VOLT:OFFSET OFFSET
Reset the TW’s output to a safe condition:
SOUR {1,2,3} :VOLT:OFFSET 0.0
OUTPUT OFF
3.8 DC LOCAL HIGH RANGE CALIBRATION
Both the measurement and output subsystems are calibrated at the same time.
Connect the DMM to the output phase of the TW to be calibrated. Set the DMM for
auto–ranging volts DC. Send the following GPIB commands to the TW:
OUTPUT OFF
OUTP:COUP DC
Wait for the TW to complete its coupling change to DC. Continue with the following
GPIB command:
SOUR:VOLT:RANGE HIGH
SOUR:SENSE LOCAL
SOUR
{1,2,3} :CURR 5.00
OUTPUT ON
SOUR
{1,2,3} :VOLT:OFFSET 0.0
Wait for the DMM to settle and record the value as RDGN1 .
Send the following query command to the TW and record the return string as MEAS1 :
MEAS {1,2,3} :VOLT?
Calculate the offset value:
VALUE1 = RDGN1 – MEAS1
Send the offset value to the TW:
CAL {1,2,3} :MEAS:LOC:HIR:VOLT:OFFSET VALUE1