Sequoia / Tahoe Series User Manual California Instruments
276 M447352-01 REV-A
FREQ 100
VOLT:ALC OFF
OUTP 1
7. Set the output current of the power supply to the low 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 supply 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.
9.2.10 Output Current Measurement AC High-Range Gain Alignment, AC-Mode
1. Connect the power analyzer for AC current measurement.
2. Connect the load to the output of the power supply.
3. Set load to the high-range resistance for 90% of the rated current, appropriate for the model that
is to be aligned. Ensure that the load setting maintains the power supply in the constant-voltage
(CV) mode of operation.
4. Enter the calibration password with the SCPI command, CAL:PASS “5000”.
5. Send the following SCPI command to select Phase-A:
INST:NSEL 1
6. Send the following SCPI commands to the power source (333 VAC range selected; ALC off):
OUTP 0
CURR:PROT OFF
MODE AC
VOLT:RANGE 333
VOLT 166
FREQ 100
VOLT:ALC OFF
OUTP 1
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