Magneto-inductive displacement sensors

Paul Boughton

Precision sensor manufacturer Micro-Epsilon has extended its mainSENSOR series of magneto-inductive displacement measurement sensors.
 
The latest addition to this growing family of sensors is a new, slimline version with an M18 stainless steel housing. The new MDS-45-M18-SA provides a longer measuring range, from 20mm up to 55mm, depending on the size of the magnet. This new streamlined design also allows increased frontal pressures of up to 400bar.

An additional groove around the housing enables the measuring system to be sealed with an O-ring, protecting the sensor from oil, seawater and other aggressive substances.

Typical applications for the MDS-45-M18-SA include hydraulic valves, attenuators and subsea hydraulics.
 
Micro-Epsilon’s mainSENSOR range operates on the magneto-inductive measuring principle. The sensor coil is supplied with alternating current, resulting in a primary magnetic field. This magnetic field induces eddy currents in the electrically conductive material arranged opposite the coil. In the field of the eddy current sensor is a special film, which attenuates the eddy current sensor depending on the strength of the magnetic field. Using this method, a linear relationship between the distance to the magnet and the output signal can be established. As printed coils can be used inside the sensor, manufacturing does not rely on any semiconductor processes.
 
As Chris Jones, Managing Director at Micro-Epsilon UK Ltd, says: “Due to simplified electronics, Micro-Epsilon is able to produce low cost versions of the sensor with printed circuit boards and basic analogue outputs, or can combine this version with a microprocessor to create a digital output sensor, including PWM, CANbus and other digital interfaces. The electronic circuit design and production is undertaken in-house at Micro-Epsilon’s PCB production facility, giving the company full design flexibility for the electronics, combined with complete control over product quality.”
 
Although the mainSENSOR uses a permanent magnet as the target, unlike Hall Effect sensors, it does not suffer from relatively low sensor accuracy or high temperature drift. mainSENSORs use Micro-Epsilon’s unique, patented measuring method, which is based on a linear relationship between the position of the permanent magnet and the output signal.
 
As well providing a simplified displacement measurement technique, mainSENSOR also offers extremely high basic sensitivity, excellent temperature stability (low thermal drift) and a maintenance-free, wear-free measurement solution.

The mainSENSOR family now includes three standard sensor ranges, including the new slimline MDS-45-M18-SA range.
 
The MDS-45-M30-SA has a 55mm measuring range and an M30 cylindrical, barrel-type stainless steel housing. The sensor weighs just 15g and can operate in temperatures up to 80 deg C. The signal output provides 4-20mA or 2-10V DC.
 
The alternative to this is the OEM version, the MDS-45-K-SA, a miniature flat rectangular PCB version of the sensor with a plastic housing, countersunk M4 screw connection and a 55mm measuring range. Signal output is 4-20mA or 2-10V DC.
 
For more information, visit www.micro-epsilon.co.uk