DIFFERENTIAL LINEAR VELOCITY TRANSDUCER

This document is a United States Patent assigned to Digital Equipment Corporation describing an improved velocity transducer for converting linear mechanical motion into an electrical signal. Specifically designed for magnetic disk recording systems, the apparatus utilizes a stationary permanent magnet supported within a closed-path iron pole piece assembly.

Key features and improvements include:

• Dual-Coil Design: Unlike prior art transducers using a single coil, this invention employs two coils connected in series and wound in opposite directions relative to the magnetic flux.
• Noise Rejection: This configuration allows "common mode" noise signals induced by external electromagnetic fields to cancel each other out, while "differential mode" motion-related signals add together.
• Performance: Testing demonstrated that this differential transducer achieved more than double the velocity sensitivity and an improved signal-to-noise ratio (by a factor of one hundred in specific tests) compared to previous single-coil designs.