A computer-based, battery powdered, data acquisition system is described, which forms part of a field-based chemical system for use with sensors generating a voltage. The equipment has been developed using complementary metal oxide semiconductor (CMOS) "low power" integrated circuit technology and is based on a multiplexed bus. One 2k-byte erasable programmable read only memory (EPROM) controls the data acquisition process. Another 2k-byte EPROM contains the monitor program, while a 2k-byte random access memory stores the data before and after manipulation. A microprocessor unit provides all the control signals used by the instrument and data are collected on a real-time basis. The electronics are housed in a self-contained box to which the sensors and an independent keyboard can be connected. The instrument can be linked with as many as eight sensors. With the use of battery-operated CMOS technology, the measurement noise level is low and analytical techniques can be used to determine low concentrations of variables in the field. The viability of the instrument has been demonstrated by obtaining extensive data on the measurement of temperature and pH. Field-based potentiometric titrations, ion-selective electrode applications and studies on battery life are also reported.