Low-cost draw wire sensor for machine builders and OEMs

Compact, reliable and cost-effective, Micro-Epsilon's MK77 draw wire sensors are suitable for integrating into products or measurement equipment produced in high volumes. The MK77 is an extension to the company's existing, well-proven MK series, developed primarily for high-volume OEM applications. Although the MK77 benefits from standard sensor technology, it can also be easily customised to suit individual applications. Potentiometric or incremental encoder outputs are available.

One of the distinctive features of the MK77 is that the housing is now moulded from plastic, resulting in a more compact, lightweight sensor that helps to minimise production costs. Machine builders and designers will benefit from a lower cost and a more compact sensor design that will open up new possibilities in machine design and cost optimisation. This also means that OEM customers can now select whether they require a metal-bodied draw wire sensor for use in harsh operating environments, or a significantly lower-cost plastic-bodied sensor that does not compromise on performance.

Production costs minimised

By using manufacturing methods that are described as 'unique', Micro-Epsilon has kept production costs for the MK77 to a minimum. The sensor drum, holder and complete housing are moulded in one piece, which means there is no separate shaft or additional bearings.

The principle of a draw-wire displacement sensor is relatively straightforward, hence its inherent reliability. The sensor works rather like a tape measure, except that with a draw-wire sensor the user does not have to read off the measurement of the extended tape. Instead, the rotation of the drum on which the steel wire is wound is measured automatically. The drum itself incorporates a long-life spring drive that ensures the steel wire is rewound.

Fast food application

Although the MK77 was officially launched in June 2007, the sensor was originally developed for a specific customer in the fast food industry. A USA-based fast food restaurant chain is now using the MK77 sensor on its oil frying tanks (for french fries) to measure the level of oil in the fresh oil storage tank. Current order requirements total more than 4000 sensors per year for this customer.

Thomas Birchinger, Product Manager for draw wire and inductive sensors at Micro-Epsilon, comments: "The customer originally had to change the oil manually when the tank [200cm x 80cm] was empty. This hot oil was considered unsafe for manual handling and so a safer, more reliable solution was sought. The machine builder of the oil frying system and storage tanks chose to use the MK77 to measure the oil level in the fresh oil feeder tank."

The frying system consists of two tanks, with fresh cooking oil being pumped slowly but continuously from the fresh oil tank to the frying equipment. Birchinger states: "The crucial factor in working with Micro-Epsilon was the MK77's excellent price-performance ratio and its inherent reliability."

Other MK sensors

The MK77 is the latest addition to Micro-Epsilon's plastic-bodied range of draw wire sensors, which already includes the MK30 and MK46 sensors.

Micro-Epsilon's range of draw wire sensors is currently being used in a diverse range of applications. In the medical industry, for example, where sensor requirements typically include long life, low protection class, high precision and constant temperature, Micro-Epsilon's draw wire sensors are being used on dentists' chairs, hospital beds, rehabilitation equipment, ambulance stretchers and X-ray systems.

In the aerospace sector, applications include: landing gear test systems; measuring simulator position; and testing of wing structures. In the automotive industry, the sensors are being used to measure engine vibration, pedal position and suspension, as well as in crash testing.

Lifting technology is another area where draw wire sensors can be used. Applications include: theatre stages; vehicle lifting platforms; lifting systems on garbage trucks; mobile hydraulic lifting platforms; and telescopic materials handling equipment.

Other more diverse applications include: positioning of saw blades; confirmation of press closure; measuring the fill level in biogas tanks and oil storage tanks; and the position of sluice gates.

For a free 31-page wire sensor selection guide, contact Micro-Epsilon.