A potentiostat based on a voltage-controlled current source for use with amperometric gas sensors

The results of comparing two potentiostat designs are presented. One is based on conventional use of a current-to-voltage converter (CVC); the second is a new design which employs a voltage-controlled current source (VCCS). The performance of the two designs in the time and frequency domains and the signal-to-noise ratio have been characterized. In the VCCS-type potentiostat, instabilities created by the CVC are eliminated. The working electrode of the gas sensor can now be connected directly to ground, improving the signal-to-noise ratio when long cables are used. The VCCS is controlled by the error voltage developed by a difference amplifier that compares the sensor bias voltage between the difference and working electrodes to a preset reference voltage. The VCCS is used to drive the counter electrode to maintain this bias level. Since the error voltage is proportional to the current in the sensor, the error voltage provides a nonintrusive measurement of current.< >