The Fluke Helios I Computer Front End is a data acquisition and control subsystem that can be used with any kind of personal or mainframe computer. The Front End combines a full range of measurement capabilities with easy programmability. It includes: o An RS-232-C and an RS-422 standard serial interface port for communication with a host computer. o A microcomputer with ROM and RAM to provide local intelligence. o Six option slots that accept any of a range of measurement and control modules, supporting a variety of both analog and digital inputs and outputs. Expansion chassis can be added to accommodate more up to a maximum of 1500 in the system. A maximum of 1000 channels can be accommodated if the Scan/Alarm option is in use. The Computer Front End is a smart intermediary between a computer and a real world measurement application. Through a standard computer interface, the Front End gathers data about physical quantities and generates control or stimulus signals. The Front End is a medium speed, highly accurate measurement and control system. It can be adapted to a very broad spectrum of applications, with a capacity ranging from a single channel in a minimal configuration to 1500 (or 1000 with the Scan/Alarm option) in a fully expanded system. A microcomputer in the Front End executes commands received from the host computer, drives the measurement and control hardware, and sends appropriate responses back to the host. The command set is a collection of high level instructions, presented in a readable and easy-to-grasp format. Channel definition commands select ranges and sensor types. From then on, automatic signal conditioning and data conversion take place for sensors as common as thermocouples, RTDs and strain gauges, or as unique as a user-defined sensor type. Thus, the Front End responds to a measurement request command by returning a value in appropriate units of measurement. Conversely, a channel set command, which assigns a value to a control output, is translated into an electrical signal.