Month: May 2018

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.

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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.

The characteristics of a particular body signal are dictated by its amplitude and frequency. The frequency of a signal can help determine the ideal rate at which to sample a particular signal, thus ensuring the resulting waveform is of the highest quality. Basically, the higher the frequency of a signal, the faster the sample rate that should be used. As an analogy – if we liken the various signals to a freeway and assume all cars are traveling in the same direction, but at different speeds, we can then determine the signal’s frequency band by looking at the slowest cars and the fastest cars. For comparison, a “slow car” would be an electrogastrogram (EGG) signal (0-1 Hz) and a “fast car” would be an electromyogram (EMG) signal (10-2000 Hz). In order to acquire the information correctly, we need to ensure the sample rate is set high enough to sweep up in our dragnet the fastest cars along with the slower cars. In the case of the EMG signal, if the sample rate is set to only 100 Hz, many of the faster “cars” would not be captured, and the definition of the upper frequency ranges would be lost in the resulting waveform. Conversely, 100 Hz would be more than sufficient to capture all of the “cars” on the EGG signal freeway. (Other frequency range examples for particular signals are: ECG = .05-100 Hz, EEG = 1-100 Hz, EOG 01.-100 Hz.) The good news is that BIOPAC sets the acquisition sample rate to a default of 2000 Hz in our  MP160 or MP36 systems for AcqKnowledge or Biopac Student Lab software, more than sufficient for most applications. That said, it’s good practice to determine the maximum frequency response of a particular signal and multiply that maximum by four times to arrive at the sample rate that will capture all the cars moving down the freeway.

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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.