A simple and inexpensive device for applying a calibration pulse when performing intracellular recording

A simple and low-cost device is described which facilitates the calibration of intracellular DC recordings in amplitude and time. A current source, optically coupled to a conventional stimulator, injects a pulse of current, across a 1-omega resistor connecting the preparation to ground. Amplitude and duration of the current pulse are determined by adjusting the voltage output of the conventional stimulator. By linking the preparation to ground through a resistor of 1 omega the background noise and the DC shifts in the voltage trace of the intracellular recording are kept to a minimum.