A self-contained calibration unit for use with intracellular recording systems

A relatively inexpensive solid state device designed for calibration of amplifiers and recorders used in microelectrode studies is described. The device is imposed between the ground electrode and the amplifier and provides three calibration signals; 100 mV DC for calibrating amplitude a variable-frequency square wave, 100 mV in amplitude use for capacitance neutralization, and a 100-mV, essentially square-wave signal with variable rate of rise and fall used for calibrating electronic differentiating circuits. The instrument is self-contained and battery powered. It was designed to remain in the circuit while recording. Calibration can be accomplished with the microelectrode in the circuit or with a dummy load.