EPM-1500 ... Research Bench Mains Digital pH/mV Meter Circuit Board Set These were the two circuit boards which comprised the electronics of the EPM-1500 research meter.  The instrument was mains operated via the on- board transformer and highly regulated power supply.  The boards were interconnected by removeable pin leads.  The very stable high-impedance front end was designed around a monolithic dual FET in a log-tailed pair configuration.  Only the best quality op-amps were utilised throughout. The instrument enjoyed great support from the New Zealand scientific community, having regard for the quality of the multi-national opposition.