BIOPAC amplifiers used with the MP160 Data Acquisition System are equipped with configurable settings designed for optimizing the physiological signal being acquired, one of which is the gain setting. What is gain? Put simply, gain refers to the amplifier’s ability to adjust the power or amplitude of an incoming signal. If an incoming signal is very strong, and the gain level on the amplifier is set too high, the signal may appear onscreen as “clipped,” resulting in loss of data. This can happen when the strength of the signal exceeds the maximum input voltage range of -10 volts to +10 volts supported by the MP160 Data Acquisition System. (Think trying to fit 20 lbs of oranges into a 10 lb bag.)
This condition, also known as “railing,” means the amplifier gain level needs to be reduced in order for the signal to fall within the maximum 20 volt peak-to-peak range. Conversely, if an incoming signal is weak or of low amplitude, the gain level will need to be increased, lest the signal appear too small onscreen for proper analysis. (Akin to trying to fill up a 10 lb bag with one or two oranges.)
A good rule of thumb for setting proper gain levels is to remember that a lower amplitude signal requires a higher gain setting, while a higher amplitude signal can tolerate a lower gain setting.
BIOPAC 100C Series amplifiers generally have four gain settings (for example, 500, 1000, 2000 and 5000, in the case of the ECG100C amplifier). A gain setting of 5000 would result in a signal amplitude 10x greater than the same signal set to a gain of 500. Although the gain settings on BIOPAC 100C amplifiers cover a wide range, the included ranges are tailored for the signal the amplifier is designed for. This means even if the gain is not optimally set, the signal should still be within an acceptable range.
AcqKnowledge software also automatically scales the incoming signal so that it fits within the graph channel, but for the highest data quality possible, attention should be paid to the gain setting of the amplifier. The good news is that AcqKnowledge software Module Setup walks you through proper configuration of amplifiers and transducers, thereby minimizing error and maximizing data quality.
For more information, view Fundamentals of Physiological Data Recording.
BIOPAC offers a wide array of wired and wireless equipment that can be used in your research. To find more information on solutions for recording and analyzing signals such as ECG, heart rate, respiration and more using any platforms mentioned in this blog post, you can visit the individual application pages on the BIOPAC website.