Configure AC or DC Measurement by Using LabVIEW and NI-SCOPE

This article will guide you to create a function to control AC or DC measurement programmatically in LabVIEW. For your information, you can configure the input channels to be DC-coupled, AC-coupled, or GND coupled. DC coupling allows DC and low-frequency components of a signal to pass through without attenuation. In contrast, AC coupling removes DC offsets and attenuates low frequency components of a signal. This feature can be exploited to zoom in on AC signals with large DC offsets, such as switching noise on a 12 V power supply. GND coupling disconnects the input and internally connects the channel to ground to provide a ground, zero-voltage reference. Refer to the specifications for your specific digitizer for input limits that must be observed regardless of coupling.

1. Download NI-SCOPE that compatible with your LabVIEW version and Hardware. The reason to download NI-SCOPE because to configure the input coupling, we may need to use niScope Configure Vertical.vi, for you reference please refer to below photo:
 
2. Once completed the installation of NI-SCOPE, kindly please reboot your PC.
3. Open LabVIEW and create New VI and go to block diagram by press Ctrl+E
4. Open a session to the oscilloscope, by right-click on the block diagram and go to Measurement I/O > NI-SCOPE > Initialize.
5. Insert niScope Configure Vertical.vi, by right-click on the block diagram and go to Measurement I/O > NI-SCOPE > Vertical.
6. Create control from vertical coupling of niScope Configure Vertical.vi, with this control you can select whether to measure AC or DC.
7. Configure the vertical parameters such as input range and offset. For more information regarding channel names, refer to Channel String Syntax in the NI High-Speed Digitizers Help.
8. Insert Configure the horizontal parameters such as sampling rate and number of samples.
9. Insert niScope Configure Horizontal Timing.vi, by right-click on the block diagram and go to Measurement I/O > NI-SCOPE > Horizontal. Configure an analog reference trigger on channel 0.
10. Insert niScope Configure Trigger Edge.vi, by right-click on the block diagram and go to Measurement I/O > NI-SCOPE > Trigger. Configure the width of the samples that will be stored in the onboard memory of the device. This will save memory space and improve fetching speed at the cost of losing resolution. Only some devices support setting this width to a lower value than the native width.
11. Initiate the acquisition.
12. Fetch the data in binary format. Select between 8-, 16- or 32-bit size samples. The samples returned will be of the actual size stored.
13. Plot the binary data.
14. Check for errors and stop if any occurred.

To have better understanding on wiring and connection you may need refer to below example VI:

From the example shows below you can see that the Input coupling can be change to AC or DC for the measurement: