Solution
The relays in the PXIe-4144 are not user-accessible. There's a property of
niDCPower called
Source:Output Connected Property which is used to toggle the output relays; however, this property is not supported in this card, as seen in
Properties Supported by the PXIe-4144/4145, and there are no plans to implement this in the near future for this card.
There's another property of
niDCPower that might come up when trying to control the outputs of this card. This property is called
Source:Output Enabled Property and it specifies whether the output is enabled (TRUE) or disabled (FALSE); however, this property does not have any effects on the output relays of the device. When the output of this card (or any SMU) is disabled by using this property, the device will not supply any power. It can, however, still sink power if the device under test (DUT) is an active device such as a power supply or a battery. Disabling the output generates a 0 V output, but does not disconnect the output. In fact, when the output is disabled, the instrument is configured to 0 V set point and current limits to 2% of range for the PXIe-4144. This is explained in further detail
Output States of PXI(e) SMUs When Output is Disabled.