Tektronix Keithley 2268 Series, Reference Manual

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Calibration and Troubleshooting Series 2268 850 Watt DC Power Supplies Reference Manual
198 2268S-901-01 Rev. A / January 2015
CALIBRATING THE OUTPUT CURRENT
Gain Calibration
To perform gain calibration:
1. Disconnect the power supply from the load.
2. Connect the output terminals to a load representing a short circuit using a precision
ammeter.
3. Turn both the power supply and the load On.
4. Set the voltage set point to maximum. Set the supply output to 90% of the nominal
current level.
5. Turn on the output power.
6. The power supply starts up in Constant Current mode.
7. Read the current value on the ammeter display.
8. Type SCPI command with current value as parameter “data”.
For example, type
: CAL: OUTP 5.07
if you had a model 150-5.6 calibrating with the
current set point set to 5.04 A and the ammeter was reading 5.07 amps.
Offset Calibration
Offset calibration of the power supply provides the best accuracy in low-range current.
To perform offset calibration:
1. After performing gain calibration, set the current to 10% from the nominal.
2. Read the current value on the ammeter display.
3. Type SCPI command with the current value as parameter “data”.
For example, you would type : CAL : OUT P: CURR 0.50 if you had a model 150-5.6
calibrating with the current set point set to 0.56 A and the actual current measured was
0.50A.
After performing offset calibration, it is highly recommended that you repeat gain
calibration.
Important:
For best results, both calibrations may be repeated several times.
To maintain the high current accuracy of the Series 2268 power supplies, user
current calibration should only be done with a high accuracy calibrated shunt
resistor of at least 0.025% tolerance.
SCPI Command
[:]CALibration[<channel>]:OUTPut:CURRent{<ammeter reading in amps>}