Reading a Voltage Signal With the SCXI-1520
Hardware: SCXI>>Modules>>SCXI-1520
Problem: How can I read a -10 to 10 volt signal using the SCXI-1520?
Solution: The SCXI-1520 is designed specifically for strain gages, so there are several steps you need to follow before you can accurately read a voltage signal:
NI-DAQmx 7.0 or later
- Create a Voltage Analog Input Task or Global Channel in Measurement and Automation Explorer (MAX).
- Under the Settings tab configure the Terminal Configuration as Differential and the Input Range as the voltage range you expect.
- Under the Device tab configure the Auto Zero Mode as None and the Lowpass Filter Cutoff Frequency as Disable Filter.
- Connect the positive lead of your input signal to the S+ terminal of the SCXI-1314. Connect the negative lead to S-.
Traditional NI-DAQ
- Set the internal voltage excitation level to zero. This setting can be found on the channel tab of the module properties in MAX. The internal voltage excitation is internally connected to the offset nulling circuitry. To make sure that the nulling circuitry is not putting an offset on your signal, set the internal voltage excitation level to zero. Alternately, you may set the voltage excitation level to a non-zero value if you intend to use the nulling circuitry to auto-zero your signal.
- Set the bridge configuration to full-bridge. This setting can also be found on the channel tab of the module properties in MAX. The half-bridge completion network is internally connected to the S- input terminal for both half-bridge and quarter-bridge configurations. This resistor network will affect your readings if not disconnected. Setting the bridge configuration to full-bridge disconnects the half-bridge completion network.
- Adjust the gain and filter settings. Gains up to 1000, which are appropriate for strain gages, will cause large voltage signals to rail. These settings can be found in the same location as the excitation and bridge configuration settings.
- Connect the positive lead of your input signal to the S+ terminal of the SCXI-1314. Connect the negative lead to S-.
Related Links: KnowledgeBase 2I7EBBJ3: How Can I Measure a Full-Bridge Transducer with the SCXI-1520?KnowledgeBase 2APDE2JW: Can I Use the SCXI-1520 to Null the Offset of a Voltage Signal?Product Manuals: SCXI-1520 User ManualProduct Manuals: SCXI-1520 Calibration Procedure
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Report Date: 06/20/2001
Last Updated: 07/23/2008
Document ID: 2AJE1KJW
