What If My DC Power Supply Is Not Reading Back the Correct Voltage or Current?

What If My DC Power Supply Is Not Reading Back the Correct Voltage or Current?

The VirtualBench DC power supply is a system of setpoint DACs and readback ADCs. Each setpoint and readback channel will have calibration accuracy and load regulation, as specified in the DC Accuracy table in the NI VirtualBench Specifications. Under normal operation, the readback channels will differ from the setpoints within the accuracy window.

The DC power supply output stage is fault protected, described in the output channel protection specification in the NI VirtualBench Specifications. In the event an output exceeds the maximum channel ratings or the temperature exceeds the environmental specifications, described in the NI VirtualBench Specifications, the thermal protection circuitry will trip and limit available output power. Remove the load from the output channels and allow the device to cool sufficiently. Once cool, test the channel in question as described below.

Validating an Output Channel

Validating Constant Voltage Mode:

1. Connect the VirtualBench Digital Multimeter (DMM) HI (red, Volts) to the output channel to test and LO (black) to ground.
2. Set the DMM to DCV, Auto Range or 100 V.
3. Set the DC power supply test channel to its maximum available output current.
4. Set the DC power supply test channel to a voltage to test.
5. Enable the DC power supply.

The DMM Volts and DC power supp voltage setpoint and voltage readback channels should agree within DC accuracy specifications, listed in the DC Accuracy table in the NI VirtualBench Specifications. The current readback should be near zero within DC accuracy specifications. The DC power supply mode indicator should read CV.

Validating Constant Current Mode:

1. Connect the VirtualBench DMM A (red, Amps) to the output channel to test and LO (black) to ground.
2. Set the DMM to DCA, Auto Range or 10 A.
3. Set the DC power supply test channel to its maximum available output voltage.
4. Set the DC power supply test channel to a current to test.
5. Enable the DC power supply.

The DMM Amps and DC power supply current setpoint and current readback channels should agree within DC accuracy specifications, listed in the DC Accuracy table in the NI VirtualBench Specifications. Voltage readback should be the burden voltage of the DMM 10 A range at the test current applied. The DC power supply mode indicator should read CC.