Sequoia / Tahoe Series User Manual California Instruments
M447352-01 REV-A 277
7. Set the output current of the power source to the high-range and 90% of the rated current,
appropriate for the model that is to be aligned, using the SCPI command, CURR < 90% of the
rated current>.
8. Perform the alignment with the SCPI command, CAL:MEAS:CURR <numeric value>. The
numeric value for the selected phase is the actual output current derived from the reading of the
external power analyzer. Ensure that the temperature coefficient of the load is low so that the
resistance value of the load does not change during the time interval required to read and enter
the external reading.
9. Send the SCPI query command, *OPC?, to determine when this alignment section has been
completed. Ensure alignment has been completed (query returns a 1) before continuing.
10. Repeat Steps 5 through 8 for output frequencies of 550 Hz, 819 Hz, and 905 Hz, or the highest
frequency of the power source model being aligned. The SCPI command, FREQ, must be
changed for each frequency, e.g. FREQ 550, FREQ 819, FREQ 905.
11. Send the SCPI command, INST:NSEL 2, and repeat Step-6 through Step-10 to align Phase-B.
12. Send the SCPI command, INST:NSEL 3, and repeat Step-6 through Step-10 to align Phase-C.
13. The calibration coefficients could be queried using the SCPI command, CAL:MEAS:CURR? ALL.
The command will return a command-separated number sequence of four calibration sets. Each
set will have the calibration frequency and the corresponding coefficient for low-range and high-
range, with the following format:
f1,dataL1,dataH1,f2,dataL2,dataH2,f3,dataL3,dataH3,f4,dataL4,dataH4.
9.2.11 Output Current Measurement AC Low-Range Offset Alignment, AC-Mode
1. Ensure that there is no load connected to the output of the power source.
2. Enter the calibration password with the SCPI command, CAL:PASS “5000”.
3. Send the following SCPI command to select Phase-A:
INST:NSEL 1
4. Send the following SCPI commands to the power source (166 VAC range selected; ALC off):
OUTP 0
CURR:PROT OFF
MODE AC
VOLT:RANGE 166
VOLT 0
FREQ 60
VOLT:ALC OFF
OUTP 1
5. Reset the low-range offset alignment with the SCPI command, CAL:MEAS:CURR:LROF 0.
6. Measure the output current with the SCPI command, MEAS:CURR?.
7. Perform the alignment with the SCPI command, CAL:MEAS:CURR:LROF <numeric value>. The
numeric value is the output current returned by the command MEAS:CURR?. Enter successive
values from MEAS:CURR? until the alignment gives a value of ≤ 1 mA(RMS).
8. Send the SCPI query command, *OPC?, after each numeric value entry to determine when this
alignment has been completed. Ensure alignment has been completed (query returns a 1)
before continuing.
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