The sensor is the starting point of a measuring chain and converts a physical measured quantity (e.g. pressure, distance, temperature) into an electrically measurable quantity (e.g. voltage, resistance). This is done by taking advantage of various electrical and / or physical effects.
The following information is provided to support you in choosing a suitable sensor. Sensors are not available at bmcm. Therefore you will find a selection of sensor manufacturers we recommend further down on this page.
You can only measure few quantities directly with DAQ systems (e.g. current, voltage). Therefore physical laws including a current or voltage relation are applied (indirect measurements).
A resistance measurement for example, is done by connecting a resistor to a constant current source and measuring the voltage drop. In order to get the correct resistance, the measured voltage has be to devided by the applied current.
Sensors "translate" physical into electrical quantities. To connect them to a measuring system, the output has to correspond with the input of the DAQ device in unit and range of values. This is done by electrically transforming and / or amplifying the signal of the passive sensor with a measuring converter or amplifier.
In many sensors, this electronic function is already included and they need their own power supply. Those sensors are called active sensors, as they convert the measured quantity into a measurable electrical quantity themselves.
Physical Measured Quantities
The following list of sensor types exclusively applies to analog measured quantities, as we focus on analog measurement technology.
|Measured Quantity||Physical Phenomenon||Sensor Type||Comments, Examples|
|temperature||temperature dependance of resistance||PT100, PT1000, NTC, PTC||nonlinear element|
|temperature||Seebeck effect (thermoelectric voltage)||thermocouple||large measuring range, nonlinear element|
|temperature||temperature dependance of semiconductors||diodes, transistors||also available as active sensor|
|temperature||pyroelectric effect||for temperature change only|
|pressure, tension||piezoelectric effect||piezoelectric element||for force and pressure changes only|
|pressure, tension, torque moment||resistance dependance of the conductor shape||strain gauge (DMS)||usually connect as measuring bridge|
|position, length, angle, distance||inductivity change of a coil when inserting a metal piece LVDT||LVDT, differential choke||measurement with carrier frequency procedure|
|position, length, angle, distance||binary encoded angle and distance sensors||angle encoder||incremental or absolute; output digital|
|angle, distance||linear potentiometer, rotary encoder||potentiometer||analog output signal|
|magnetic induction||echo voltage with constant current||echo sensor||available as active integrated wiring|
|acceleration, velocity||tension of metal plates in semiconductor component||semicond. strain gauge||uni- or multidimensional sensor|
|acceleration, velocity||piezoelectric effect with a seismic mass||piezoelectric element||e.g. airbag sensor|
|luminous intensity||photonic stimulation of semiconductors||photodiode, phototransistor||available as passive and active sensors|
|luminous intensity||change of self-conductivity||photoresistor|
|current||voltage drop at a resistor||shunt||galvanic connection to the meas. current|
|current||measurement of the Hall||echo sensor||el.isolated from the meas. current|
|humidity||semiconductors, capacitive sensors||passive elements|
|sound, sound level||electrodynamic and capacitive microphones||microphones|
|filling-level||capacitive and optical measurement||active sensors|
|rotational speed||optical and inductive processes||speed encoder||digital and analog sensors|
|motion||optical and inductive processes||motion detector|
The following table provides a small selection of sensor manufacturers. This is just a selection and does not imply any judgement.
Please note that we are not responsible for the contents of the linked sites and we do not check them regularly. In many cases, the mentioned semiconductor manufacturers do not have their own sales department.
|All Sensors GmbH||x||high|
|B+B Sensors (HYGROSENS)||x||high|
|disynet (German website)||x||x||x||x||medium|