The Data that I Acquired in BioBench is Noisy
Primary Software: Other NI Software>>BioBench
Primary Software Version: 1.0
Primary Software Fixed Version: N/A
Secondary Software:
Problem: I am performing data acquisition (DAQ) with BioBench. My acquired data is noisy. Is there anything that I can do about this?
Solution: There are many reasons why your data may appear to be noisy or distorted. Some of these reasons are related to hardware configuration and some are related to software configuration.
- Cabling - Ensure that all cables are connected correctly and securely.
- Improper Ground - Check the ground references of your signal. Ensure that the NI-DAQ Configuration Utility shows your hardware’s analog input reference mode to be properly configured. Refer to the user manual of your DAQ hardware for details about analog input reference modes and how to connect your signals.
- Improper Voltage Range - In the Channel Configuration dialog box presented in Chapter 2 of the BioBench User Manual, Setting Up Your System, you specify for each signal the minimum and maximum voltages you expect. If these values are inaccurate, BioBench may acquire noisy or incorrect data.
- Signal Is Too Small - Your signal can be of such a small voltage level that noise distorts the signal. Typically, in this case you should be using data acquisition hardware which applies a gain to amplify your signal and thus reduces this distortion. Not all DAQ hardware is capable of applying gain. If you do not have a means to apply gain to amplify your signal, you cannot acquire signals that have small voltage levels. Refer to the user manual of your hardware for instructions on configuration.
- Mixed Signals - You may be simultaneously acquiring high-level and low-level signals. Low-level signals (<1 VDC) typically require that gain be applied by the DAQ hardware, to reduce noise. Some DAQ hardware does not allow you to apply gain to some signals and not to others. In this case, you should use DAQ hardware that allows you to apply a different gain to each signal. Refer to the user manual of your hardware for instructions on configuration.
In addition to addressing the preceding possible cases, you can also try the following measures:
- Software Filtering - BioBench allows you to reduce noise in your signal caused by 50/60 Hz power sources by applying a 50/60 Hz notch filter. See Chapter 3 of the BioBench User Manual, Acquiring Data, and Chapter 4, Analyzing Data, for information about enabling the BioBench software filtering.
- Hardware Filtering - It is always best to remove noise from your signals before the signals are acquired in BioBench, if possible. You can design a hardware filter if you have the expertise to do so. National Instruments manufactures a wide range of signal conditioning products to help you connect, condition, and measure your sensors and signals with the personal computer.
- Increase Sample Rate - In some cases, the noise you see may be caused by undersampling. Undersampling means that you are not sampling fast enough to acquire your signals correctly. Sometimes increasing the sample rate can improve the signal.
This information can also be found in the BioBench User Manual.
Related Links: BioBench User Manual
BioBench Support
Attachments:
Report Date: 12/18/2000
Last Updated: 03/06/2003
Document ID: 24H9OM7Z
