FLIGHT TEST DATA ACQUISITION SYSTEM

Abstract

This paper describes a data acquisition system with integral signal conditioning capability. It is a distributed bus oriented system which greatly reduces the amount of wiring and structural penetrations required in previous systems used for this purpose. The system interfaces with virtually all of the transducer types existing on operational aircraft as well as those typically used for flight testing and proofing such as the strain gauges. It outputs data in digital form to a central unit which combines this data with other aircraft operational parameters for recording on tape or telemetry to the ground. The system consists of a remote multiplexer (RMUX) which provides the formatting and central processing functions and has provision for 16 plug-in signal conditioning modules. It also has provision for up to 20 external multiplexers (EMUXes) which are designed to service a cluster of like sensors in a local area. EMUX types include bridge, thermocouple, and a highly integrated pressure scanner unit. Signal conditioning and processing functions include input transient protection, variable blocks of gain, analog pre-sample filtering, and precision bandlimiting using digital techniques . The penalty for moving the acquisition units to remote locations on the aircraft as compared to previously used cabin mounted equipment is a much more severe environment. Temperature extremes and vibration are particularly severe around the engines. Because of the planned use on operational aircraft, provisions to prevent lightning propagation to the cabin are a significant future.