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How Does BioBench Set the Channel Gain on My Data Acquisition (DAQ) Board?

Primary Software: Other NI Software>>BioBench
Primary Software Version: 1.0
Primary Software Fixed Version: N/A
Secondary Software:

Problem: How does BioBench set the channel gain on my data acquisition (DAQ) board? I understand that my DAQ board has a 16-bit Analog to Digital Converter (ADC) with a programmable input amplifier to match the input voltage to the full scale digital range of the board. Does BioBench adjust the amplifier gain or does it run with fixed gain? If the gain is changed by BioBench how do I determine what it is?

Solution: Channel gain is set automatically by BioBench. When you enter the Min and Max values for Signal Voltage Range in the Channel Configuration (page 2-8 of BioBench manual), BioBench calculates the maximum gain that can be applied to your signal to stay within the DAQ board's input range. Once the data is collected, BioBench then corrects for this gain setting and your actual signal is displayed.

For example, if you expect to read in a signal with a +/- 1 V voltage range, you would enter -1 for Min and +1 for the Max value in the Signal Voltage Range in the BioBench Channel Configuration. If your DAQ board has a +/- 10 V input range, BioBench will automatically have the NI-DAQ driver set a Gain of 10 on the board's amplifier so that all 16 bits of your ADC can be utilized to achieve a high resolution for your signal. BioBench will then handle for this gain setting and properly display your signal in the +/- 1 V voltage range. Therefore, you don't need to worry about accounting for the gain yourself.

If your signal goes above or below the +/- 1 V that you specified, you will experience clipping. Therefore, you want to pick Min and Max values that will maximize the gain that can be applied to your signal without experiencing clipping.

Related Links: BioBench User Manual
BioBench Support


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Report Date: 01/09/2001
Last Updated: 03/06/2003
Document ID: 258AM37Z

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