Incremental Quadrature

The quadrature interface has its origins in incremental measurement systems. In these systems, the scale markings are applied to a glass plate or strip, which is scanned using optical systems. A key feature of a quadrature interface is that the incremental position measurement system provides two signal rails: A and B pulses, which exhibit a positive or negative phase shift of 90° depending on the direction of motion. During motion, this results in four counting edges per period (A↑, A↓, B↑, B↓), effectively quadrupling the resolution compared to the basic optical grating.

The number of A or B pulses is a measure of the distance traveled; the pulse width of the A/B pulses therefore depends on the travel speed.

In addition, optical systems usually have a reference track that emits a signal only once along the entire measurement path to establish a reference for the incrementally determined position. This is necessary in order to derive an absolute position from the subsequent A/B pulses.

Our absolute displacement and angle sensors, such as magnetostrictive displacement measurement systems, do not require a reference run. A magnetostrictive displacement measurement system with an incremental quadrature interface transmits the correct number of A/B pulses corresponding to the current absolute position upon request.