Going the distance

A range of displacement measurement sensors has been developed that combine robustness and measurement performance with the latest printed coil and permanent magnet technology. Micro-Epsilon's new mainSENSORs family of Magneto-inductive displacement sensors not only benefit from having an extremely compact design relative to their measuring range, but also offer OEMs an attractive price-performance ratio for mid-to-high volume applications. According to Chris Jones, managing director of Micro-Epsilon (UK): "This development really has been born out of the demand from high-volume OEM customers for high-accuracy sensors at very low prices…Our engineers were looking at ways they could develop the core technology into a simpler format and this is the latest development along those lines." Originally developed by Micro-Epsilon as a high-volume, low-cost solution for load detection in washing machines, at the core of the sensor technology is Micro-Epsilon's proven eddy current sensor technology, which provides the new sensor with robustness, high speed and high-resolution measurements. However, it is how Micro-Epsilon has applied and combined this proven technology to the new sensor that provides users with several technical advantages. The eddy current technology conventionally uses a wound coil and uses very complex electronics to measure distance or the energy loss across the coil. In addition, temperature compensation was complicated by the fact that the coil of wire that changes its output as it heats and cools. Says Jones: "Recent innovations in printed coil technology enabled us to produce – effectively on a PCB – a flat coil…There are other printed coil developments out there, but this enabled us to produce the sensor element at a very low cost and we've combined that with a special material that is patented, which sits in front of the coil and amplifies the signal of the magnetic properties from the target. "The clever part is that we've combined the flat coil technology with this new material, which has enabled us to generate relatively simple electronics." While Jones is unwilling to be any more explicit about the nature of this 'special material' at this stage (preferring to refer to it as a "special film"), he is unequivocal about the benefits that customers will see from it, saying: "At that price level, they'll see a significant improvement in accuracy and resolution. With the lead sensor we're able to take resolutions down to single microns. We've got the core technology now and we can customise it to the customer's needs. You may find that the customer wants very high resolution and we can calibrate a reduced measurement range, for example. Or you may find that the customer thinks the core sensor's great but they want a particular interface like CANbus. So where it comes into its own is it's a modular design with very high accuracy for its price level. Another significant factor in the new sensor, according to Jones, is its compactness relative to competitive products. He says: "What's revolutionary here is the dimensions of the metal cylindrical sensor. Contained within that sensor are all the conditioning electronics. Everything is self-contained. Up to now, for a non-contact displacement sensor with micron resolution, the current sensors – even Micro-Epsilon's eddy current sensors – you need external electronics." The first standard industrial sensor in the mainSENSORs family is the MDS-40 M30, which has a 40mm measuring range and an M30 cylindrical, barrel-type stainless steel housing. The alternative to this is the OEM version, the MDS-40MK, a miniature flat rectangular PCB version with a plastic housing and a 40mm measuring range. The signal output provides 4-20mA or 2-10V DC. Micro-Epsilon already has a number of 'lead-in' customers for the technology. The success we've had in industrial and hydraulic markets. We are a strong player particularly in germany working with many of the hydraulic subsystems suppliers – the valves suppliers, for example. Long-standing relationship with Moog. Hoping to build on and develop that in the future.