A multichannel system for acquisition of signals recorded by thin film microelectrodes from invertebrate peripheral nerve

When making recordings from peripheral nerve with high impedance microelectrodes (>1MΩ), high impedance, high gain amplifiers are required. In order to analyse the recorded signals from multichannel microelectrode devices, it is desirable that the amplifier and filter channels used match as closely as possible, and that the data be stored by computer for off-line analysis. A five channel system is described for this purpose. The instrumentation was designed with off-the-shelf components, to have a matching between channel gains of better than 3% and the frequency characteristics of the Butterworth filter stages employed to match to 2%. Input resistance was designed to be 100 MΩ, gain switchable from 5000 to 75000 times, and bandwidth of 10 Hz or 100 Hz to 10 kHz. The system noise (including the electrode) was measured experimentally to be of the order of 15 μV rms (r.t.i). Data acquisition was performed by a PC, sampling each channel at up to 40 kHz, with custom software written in LabVIEW