Can I Use the SCXI-1520 to Null the Offset of a Voltage Signal? Hardware: SCXI>>Modules>>SCXI-1520
Problem: I know the SCXI-1520 can null a strain gage, but I'm using this module to read a voltage signal. Can I still use the nulling circuitry to compensate for an offset on my voltage signal? Solution: Yes this can be done, but there are some pitfalls you should take care to avoid. The first step is to be certain that the module is properly configured to read a voltage signal. See KnowledgeBase 2AJE1KJW "How Can I Read a Voltage Signal With the SCXI-1520?" (linked below) for more information. The most important step in this case is to set the bridge configuration to "full-bridge". The nulling circuitry is internally connected to the excitation voltage, so to use the nulling features you must set the voltage excitation to a non-zero level. In choosing an excitation level, you may trade nulling range for nulling "code width" (the smallest voltage step for the nulling circuitry). A high voltage excitation level will give you a large nulling range, but also a larger code width. A small voltage excitation level will give a very precise code width, but a smaller nulling range. Try to set the excitation level just high enough to null the offset that is present. See the SCXI-1520 User Manual (linked below) for a more detailed explaination of nulling ranges. Connect the signal input terminals (S+ and S- on the SCXI-1314) to ground. If you are using an external power supply, connect the power supply ground to both S+ and S-. If you are using the SCXI-1520 built-in voltage excitation, connect both S+ and S- to chassis ground. The SCXI-1314 does not have a screw terminal for AIGND, but you can access chassis ground at the case screw located at one end of the strain-relief bar. You are now ready to perform the nulling operation. This can be done through the Strain Gage virtual channel, or through LabVIEW. See the SCXI-1520 User Manual for more information. Once the nulling operation is complete, simply connect S+ and S- to your voltage signal. Any voltage offset has now been hardware-compensated. Related Links:
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Report Date: 06/26/2001 Last Updated: 03/17/2008 Document ID: 2APDE2JW |
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