Automation of Single-Axis Floated-Gyro Drift Measurement

This paper describes the technique and equipment developed for automating measurement of the drift rate of precision single-axis floated gyros. The basic construction principles of singleaxis floated gyros are described and illustrated. The sources and components of drift are then discussed and defined. The random component of drift is shown to be a useful measure of gyro quality and is, by reason of its definition, suited to automatic testing techniques. The equipment used to measure the random component of drift consists basically of a single-axis servo table (in which the gyro to be tested is mounted), the servo table and gyro operating circuitry, and the programming and readout devices. Although adaptable to a variety of situations, the equipment is designed specifically to apply the "cogging" or repositioning type of single-axis gyro-drift test. The servo table is slaved to the gyro output so that the table angular rate is equal to gyro input plus gyro total drift. Two microsyns (rotary differential transformers) are attached to the table shaft with their null positions spaced at an accurately known angle. The unique phase characteristic of the microsyns is used to gate a precision frequency to a time-interval meter and a digital recorder. With a component of Earth Rate as input to the gyro, the time required for the servo table (and gyro) to process through the accurately-known angle is measured a number of times. The standard deviations of the average rates through the angle is taken as random drift. The time data is printed out in digital form for transfer to punched cards and digital processing. The application of the equipment to the development and production testing of precision single-axis floated gyros provides a means of accumulating large quantities of precise data in a relatively short period of time for a reliable statistical measure of gyro-production quality.