Glossary

Absolute measuring systems

Precise determination of position

Absolute measuring systems output information on the position of a measuring scale in the form of a digital signal. This numerical value is unambiguous over the entire resolution range. Unlike incremental rotary encoders, absolute rotary encoders can therefore output the exact position value immediately after power up, without referencing and without moving the rotary encoder's shaft.

 

CNC

Computerized Numerical Control

Computerised Numerical Control (CNC) is an electronic method for the control and regulation of machine tools (CNC machines) and the related devices used (controller, computer). (translated from: Wikipedia in German)

Incremental measuring systems

Precise speed acquisition

Incremental measuring systems detect both rotational and linear motion of a measuring scale. Unlike absolute rotary encoders, however, they only measure the position change since sensor power-up. If the sensor has a separate signal output for a zero index, it is also possible to determine the position by means of a reference search routine.

 

MR sensor technology

Magnetoresistive sensor technology

Magnetoresistive effects ("MR effects") were discovered in the middle of the 19th century by William Thomson, 1st Baron Kelvin. They describe the change in the electrical resistance of a material due to the application of an external magnetic field. The effect of the externally applied magnetic field on the electrical behaviour of a solid body is very heavily dependent on which of the known MR effects is active.

A differentiation is made, among others, between:

• The anisotropic magnetoresistive effect ("AMR effect"),
• The giant magnetoresistive effect ("GMR effect") as well as
• The planar Hall effect.

The utilisation of these effects in sensors only became possible with the development of thin-film technology in the 1980s.

MTTF

Mean Time To Failure

MTTF is the abbreviation for Mean Time To Failure; it is also termed to mean service life or expected value for the time to failure. This is a statistical parameter that does not guarantee a failure-free period, but that instead is based on experience or tests.

MTTF-figures became important above all due to the European standard EN ISO 13849-1, as they are used in the conformity assessments related to machinery safety.

Resistance thermometer

Temperature measuring system

Conventional thermometers measure the temperature based on the change in the length or volume of a substance and are only suitable for use as indicating measuring instruments. Resistance thermometers utilise the change in the electrical resistance of metals as a function of the temperature to measure the temperature and generate an electrical signal. For this reason they are particularly suitable for usage in industrial measuring systems.

Pure metals exhibit greater resistance changes than alloys and have a relatively constant electrical resistance temperature coefficient. For this reason platinum is used in most cases for precise measurements, as thermometers can be manufactured from this metal with particularly low error limits.

Platinum resistance thermometers for industrial usage comprise a measuring insert in a jacket for protection against corrosion. The measuring insert is often wired to a connection head from where the thermometer can be connected via cables to an external electrical measuring system.