Why Am I Getting Noisy Measurements with My SC-2345 Signal Conditioning Modules?
Hardware: SCC>>Carriers>>SC-2345
Problem: I have an SC-2345 box with one or more signal conditioning modules. I am able to read from the modules, but I get inconsistent or noisy readings. Shouldn't the signal conditioning take care of the noise for me?
Solution: Noise problems are often one of the most difficult problems to diagnose and troubleshoot. The first thing you should do is double-check the specifications for your signal conditioning modules. Refer to the Related Links below to find the most up-to-date manual for your modules. Make sure your hardware is capable of the accuracy your measurements require. After that, there are several things you can try to eliminate the noise:
- Ensure that your SC-2345 is properly setup in Measurement and Automation Explorer (MAX). Configuring the SCC system using MAX should automatically set the E-Series DAQ device analog input mode to Nonreferenced Single Ended (NRSE). Note that if you inadvertently set it as differential, you may receive noisy or unusual signals if any at all. You can set the analog input mode in MAX for your Traditional NI-DAQ device by going to My System » Devices and Interfaces » Traditional NI-DAQ Devices » <Your Board>. Right-click and select Nonreferenced Single Ended under Properties » AI » Mode. Note that you do not need to do this if you are using DAQmx (E-Series or M-Series).
- You can add additional hardware filtering to your measurement on top what your SCC module may provide. Using an SCC-LP low pass filter module in series with your module can remove unwanted frequency components. Refer to the Related Links section below for more information on how to do this.
- Depending on the programming environment you are using to develop your application, you can apply various software filtering techniques to your data. By acquiring more data points than you need, you can use averaging to help eliminate high frequency noise. Again, refer to the Related Links below for more detailed information on how to do this. You may also implement Butterworth, Chebyshev, Bessel, etc. filters in your code. In the Professional and Full Development versions of LabVIEW, these VIs may be found in the Functions Palette under Analyze » Signal Processing » Filters. LabVIEW 7.0 and later also includes a Filter Express VI under Analyze » Waveform Conditioning.
- There are three power options for the SC-2345: the SCC-PWR01, SCC-PWR02, and SCC-PWR03. The first option uses power from your DAQ board. The second two options use an external power supply. Sometimes your external ground reference can be noisy. Try plugging the power supply in different outlets.
If you are still experiencing noise after trying these techniques, double-check your hardware setup (including wiring) for both the SC-2345 and any modules you have installed. You may also
Request Support from an engineer.
Related Links: KnowledgeBase 31FH2UW0: How Can I Create A Custom Excitation Voltage For My Signal Conditioning System? KnowledgeBase 2V4F65DF: Unexpected Voltage Signal Detected on SC-2345 Chassis KnowledgeBase 2FK8NNFT: How Can I Filter Out 60 Hz Noise When I am Using the SCC-SG04 Full Bridge Strain Gauge Module? Developer Zone Tutorial: Measuring Strain with Strain Gauges Developer Zone Tutorial: Reducing the Effects of Noise in a Data Acquisition System by Averaging Product Catalog: NI SCC-LP Series -- Lowpass Filters Product Catalog: NI SCC Modules Product Manual: Signal Conditioning SC-2345/2350 Carrier User Manual
Attachments:
Report Date: 10/26/2004
Last Updated: 10/12/2007
Document ID: 3EP8BMS9
