MA-821/RSP Four-Channel Moving Averager

MA-821/RSP 4-Channel Moving Averager

The MA-821/RSP is the latest incarnation of one of our first commercial instruments. The Moving Averager (MA), or Paynter filter, has long been used to quantify multi-unit nerve and muscle activity.1  For example, the MA is strongly correlated with the force of contraction of a muscle at any given time. It employs a precision, full-wave rectifier and third-order filtering to create a smoothed envelope around the nerve or muscle burst. This approach has the advantages of a high degree of smoothing, while retaining a fast dynamic response, so no details of the electrical activity are lost. The time constant (TC) determines the amount of smoothing. The Moving Average should not be confused with "leaky integrator" or other simplified first-order circuits that do not preserve the dynamics of the signal.2

Convenient Features: The MA-821/RSP is a rack-mountable instrument with four independent signal processing channels. Each has pushbutton-selectable time constants, so the averaging time can be changes instantaneously. The gain and offset is adjustable using panel mounted controls. Input, rectified output, and MA output jacks are located on front and rear panels for convenient rack wiring.

Programmable Time Constants: This new version of the instrument is completely redesigned, and features all-electronic switching of the three Time Constant Modules included with each channel. A microprocessor and non-volatile memory store the settings, and restore them the next time the instrument is used. The standard TC's provided are 50, 100, and 200mS. The time constants are programmed using interchangeable Time Constant Modules (three per channel), so any values in the range 10 - 500mS can be specified. These modules are available separately (Part No. MA-821-TCM), and can be changed by the user as needed.

Data sheet: Please click here for a complete data sheet in pdf format.

1. Gottlieb, G.L. and Agarwal. Filtering of Electromyographic Signals. Am.J.Physical Medicine 49(3):142-146, 1970.
2. Hopp, F.A., J.L. Seagard, and J.P. Kampine. Comparison of four methods of averaging nerve activity. Am. J. Physiology 251:R700-R711, 1986.

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Last modified: October 31, 2012