Glossary · Sensors and measurement
Displacement measuring system
Also known as: Linear measuring system, Length measuring system
German: Wegmesssystem
In industrial automation, a displacement measuring system is the combination of sensor, scale or measuring element and evaluation electronics that determines a linear position or travel of a machine part and provides it to the controller.
- Sensors
In one sentence
A displacement measuring system determines the linear position or travel of a machine part and provides it to the controller as a measured value.
Example
A glass-scale displacement measuring system on the X axis of a milling machine gives the CNC the actual position of the table, independent of spindle errors.
How it applies
- Engineering: Common principles are optical and magnetic scales, magnetostrictive sensors, potentiometers and LVDTs. The system is specified by measuring length, Resolution, accuracy, interface (analog, incremental, absolute serial) and environmental resistance.
- Commissioning: Direct measurement at the moving part eliminates errors from the drive train, but the scale must be aligned and the reference or offset set.
- Maintenance: Contamination of open scales and damaged cables are common causes of position errors. Replacement usually requires re-referencing.
- Documentation: State which measuring system closes the position loop of each axis and what has to be adjusted after replacement.
Displacement measuring system vs. displacement sensor
A Displacement sensor is the sensing element. The displacement measuring system also includes the scale, mounting and evaluation electronics that turn the sensor signal into a usable position value.