Can the PXI-4110 be used as a Current Source?Hardware: Modular Instruments>>Power Supplies>>PXI-4110
Problem: I want to be able to use the PXI-4110 as a current source. How do I configure it to output a constant current? Solution: The PXI-4110 can act as a current source. There are two ways to output a constant current with the PXI-4110. In the first method, set the PXI-4110 to output DC Voltage and have the load attached to the device attempt to draw more current than is allowed by the programmed current limit. For example, you have a 10 ohm resistor connected to the PXI-4110. Set a voltage of 5 volts across that 10 ohm resistor, and you will see 0.5 A flow through it. In that way, the 4110 is functioning as a voltage source. To change it to a current source, set the current limit to be less than 0.5 A. For instance, you could set a current limit of 0.1 A (with the voltage level set to 5 V). This will limit the current from the PXI-4110 to be 0.1 A. You are limiting the current to a value less than Ohm's Law (V = IR) would have naturally allowed. To set the current limit this way in LabVIEW, use niDCPower Configure Current Limit.vi. After you set the limit appropriately and enable the output, the status indicator on the front of the 4110 will be amber signifying that the channel is functioning in constant current mode. If the status indicator is green then the 4110 is acting as a voltage source and is not limiting the current.
The example NI-DCPower Generate DC Voltage.vi shows how to configure a PXI-4110 for constant voltage mode. This example can be found in Windows in the path <LabVIEW>\examples\instr\niDCPower where <LabVIEW> is your current LabVIEW directory. Beginning with NI-DCPower 1.2, support for setting a constant current or voltage output from the PXI-4110 is included in the driver. This is done by setting the output mode of the PXI-4110 to be DC Current. In this case, as long as the voltage drawn by the load is less than the set voltage limit the desired current will be output.
The example NI-DCPower Generate DC Current.vi can be found in the same path as above. This example shows how to configure your PXI-4110 for constant current mode using the built-in functionality. Related Links: Developer Zone Tutorial: Programmable DC Power Supply and Precision DC Source Tutorial Attachments:
Report Date: 03/13/2007 Last Updated: 05/05/2009 Document ID: 47CDOCE5 |
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