This document provides step-by-step instructions for wiring and configuring your NI DAQ device for generating analog output signals. Before you begin using your DAQ hardware, you must install your application development environment and NI-DAQmx driver software. Refer to the Installing LabVIEW and NI-DAQmx document for more information.
Many NI DAQ devices can generate voltage signals. Multifunction DAQ devices typically have two or four analog output channels. Dedicated analog output or CompactDAQ devices may have more. You can generate single sample DC signals or time-varying multiple sample signals.
With AO reference selection, you can set the analog output range. The analog output range describes the set of voltages the device can generate. The digital codes of the digital-to-analog converter are spread evenly across the analog output range. So, if the range is smaller, the analog output has better resolution; that is, the voltage output difference between two consecutive codes is smaller. Therefore, the analog output is more accurate.
The analog output range of a device is all of the voltages between:
–AO Reference and +AO Reference
The possible settings for the AO reference depend on the device model. For some models the AO reference is always 10 V, making the analog output range equal to ±10 V. For other models, you may select from pre-determined voltages (such as 10 V or 5 V) or an external voltage reference (APFI or AO EXT REF terminals).
You can connect an external signal to APFI terminals to provide the AO reference. The AO reference can be a positive or negative voltage. If the AO reference is a negative voltage, the polarity of the AO output is inverted. The valid ranges of APFI are listed in your device specifications. You can use one of your device’s AO channels to be the AO reference for a different AO signal. However, you must externally connect this channel to APFI.
Note that when using an external reference, the output signal is not calibrated in software. You can generate a value and measure the voltage offset to calibrate your output in software.
Before connecting any signals, locate your device pinout.
Figure 1. Device Terminals Help
The following terminal types correspond with analog voltage generation:
You can use MAX to quickly verify the accuracy of your measurement system Set Up. With an NI-DAQmx Global Virtual Channel you can configure an analog output without any programming. A virtual channel is a concept of the NI-DAQmx driver architecture used to represent a collection of device property settings that can include a name, a physical channel, terminal connections, the type of measurement or generation, and scaling information.
Follow these steps to begin:
Figure 2. Creating an NI-DAQmx Virtual Channel
Figure 3. Device Physical Channels
Figure 4. Setting Up a Voltage Output Channel in MAX
Signal connections vary depending on your device, connector block, and signal conditioning module. The following figure shows how to make analog output connections for a typical NI device.
Figure 5. Analog Output Connections
Use your NI-DAQmx global virtual channels to test your outputs.
Figure 6. Updating a Virtual Channel in MAX
You also have the option of saving your NI-DAQmx Global Virtual Channel should you wish to refer to this configuration screen again in the future.