Using an RX and RA16PA for ABR acquisition in BioSigRP

Tech Note: TN0840
Product: BioSigRP
Version: All
Date Added: 2008-12-01


When using a Medusa preamplifier (RA16PA, RA16SD, RA4PA, or RA4SD) with an RX device for acquisition in BioSigRP, there are several issues that should be addressed.

Voltage Scaling and Artifact Rejection

BioSigRP sets its input voltage range according to the acquisition device. For RX devices this is ±10 V. However, the voltage range of the Medusa preamplifier is ±4 mV. This discrepancy between the actual and expected input voltage range renders the BioSigRP artifact rejection feature ineffective. The smallest artifact detectable in BioSigRP would be 1% of 10 V or 100 mV. This is well outside the possible range of values that can be acquired from the Medusa preamplifier.

Digital Control Bits are not Automatically Configured

The digital I/O on RX devices are programmable as either inputs or outputs and must be configured accordingly before they can be used with BioSigRP.

Specific RX Device Overhead Delays

When acquiring digitized signals from a Medusa preamplifier, additional overhead delays appear on RX devices. These delays are slightly longer than those present on RP devices such as the RA16BA Medusa Base Station.

Note on Delays

Overhead delays as well as any DAC and ADC delays are unaccounted for but will not affect recordings, especially at higher sampling rates.


An RX compatible circuit has been provided which corrects the voltage scaling, artifact rejection, and digital control bit issues. The circuit can be downloaded here.

To use the new circuit file in BioSigRP:

  1. Extract the contents of the zip file.

  2. Open the RX_ABR_ACQ folder.

  3. Read and follow the directions in the Readme.txt file.

  4. Run BioSigRP.

  5. Configure the acquisition device by loading the newly added circuit file Record25Kx2(RX).rco as the intended Acquire RCO in the BioSigRP Acquisition Setup dialog box.


When using the Medusa preamplifier for acquisition in BioSigRP, the RA16BA Medusa Base Station can be used to avoid issues related to voltage scaling and artifact rejection.