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Laser Metric Systems, Inc. (LMS) designed its first fringe counting system back in 1982. The PRM-001 was a digital up-down whole fringe counter with analog sub-fringe interpolation. It was designed for single-frequency lasers. A fringe-count results from a displacement of one-half wavelength of laser light. For a HeNe laser this is nominally 0.316 micrometers (12.5 µ inches). To measure displacements smaller than one fringe, a sub-fringe system is needed. Analog sub-fringe systems suffer from drift and interpolator inaccuracy which limits their performance. Also, single-freqency laser interferometers can suffer from amplitude drift which affects interpolator accuracy.

Stabilized lasers are needed to make accurate and repeatable measurements over long ranges. Two-frequency lasers, such as Agilent’s HP5517B, provide for the highest fringe counting accuracy. The PRM-004 series is designed for two-frequency lasers. They provide continuous readings of position by accurately measuring the Doppler-frequency, or equivalently, phase-change of transducer signals. These systems use our proprietary all-digital approach to phase sensing. By using an all-digital method, long-term accuracy and stability is guaranteed.

PRM-004 Series

The PRM-004 Series is available in ISA or PCI bus. Signal inputs are either single-ended 50 ohm (BNC) or differential (shielded- twisted pair).

The high sampling rate of 100 MHz allows tracking of signals up to 50 MHz and velocities of 3m/sec.

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Description and Specifications in pdf format

PRM-003 (Obsolete)

PRM-004-ISA-SE is a replacement for PRM-003.

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