This report describes a portable, intrinsically safe data acquisition system designed specifically for use in underground coal mines. The system is designed for high resolution and stability, and can accept a wide variety of transducer types without modification or accessories. Input units may be easily added to the system to expand it to a maximum of 240 input channels. Up to one megabyte of measurement data can be recorded by the system's data logger, which uses internal solid-state memory. Stored data can be transferred directly via modem to a host computer or copied into another unit for transportation to the surface. A user-friendly menu system displayed on a hand-held terminal allows simple control of recording and data transfer functions. All system units are designed to meet drop-test, watertightness, and other environmental criteria to enhance reliability in field use. The report includes photographs of the equipment and plots of data taken in laboratory and field tests. It also discusses system design considerations, the electronic design of each system unit, and system firmware and documentation.