New modular draw wire sensors include models with plastic cables

Micro-Epsilon''s rapidly growing wireSENSOR family has been redesigned into modular components, enabling more compact, lightweight, low-cost products to be available for OEMs. These modular designs also mean that Micro-Epsilon is able to supply direct to customers from stock, on rapid deliveries for virtually any measurement range from 50mm up to 50m, as well as any output from analogue (potentiometric, current or voltage), to digital encoder (incremental, absolute, SSi, Profibus or CANopen). Draw wire sensors can also be custom-engineered by Micro-Epsilon to suit specific high-volume OEM applications.

The wireSENSOR MK88 draw wire sensor, for example, offers users a combination of compactness, low cost and a large measuring range. The sensor was developed specifically for high-volume OEM applications such as mobile cranes, fire and rescue vehicles, mobile working platforms and scissor lifts, but can also be supplied in small quantities from stock for low-volume applications.

Weighing just 400g (including the cable), the MK88 has a very compact sensor housing that measures just 88x90x90mm. The sensor is available in three measuring ranges, 2300mm, 3500mm and 5000mm, each with output options of potentiometric (P), 0-10V (U) or 4-20mA (I). The MK88 comes with an integrated cable, but this can be changed to a connector in OEM applications if required. The sensor can also be supplied as a mechanical-only option for mounting to the user's own encoder. A universal encoder mounting plate is used to mount the sensor to the encoder.

For OEMs, the MK88 offers an attractive combination of compact size, robustness, a large measuring range and low cost. The sensor's compactness also enables it to be retrofitted easily to existing installations or mounted where the available space is tight.

The MK Series of draw wire sensors all benefit from a PA-coated stainless steel wire and a high-strength, glass fibre-reinforced plastic housing. This results in a very robust sensor that is suitable for all outdoor applications, with a maximum protection class of IP65. Operating temperature is from -20 to +80degC, although a special version can be requested that operates at temperatures down to -40degC. The MK88 currently uses an aluminium protection cap, but will shortly be available with a plastic cap as standard, with the aluminium cap available as an option.

Integration in hydraulic cylinders

Draw wire sensors can be mounted externally to hydraulic cylinders to measure piston position or displacement. After piston stroke lengths of around 1m, it becomes very expensive to deep-bore drill the piston rod to accept an in-cylinder sensor such as a magnetostrictive or LVDT sensor. Using draw wire sensors is particularly beneficial since it eliminates the high costs associated with having to deep-bore drill the piston rods using specialist equipment. The draw wire sensors can be used in most applications, irrespective of cylinder stroke length. The long stroke P96, P115 and P200 wireSENSORs are suited for these types of applications, including off-highway vehicles, mobile cranes, lifting platforms and elevators. The P series long range sensors are said to be very compact compared with alternative sensors and have a less complex mechanism used for winding the wire around the drum. This results in a much better sensor life and also reduced unit cost.

Micro-Epsilon is also launching a new version of its wireSENSOR P85 draw wire sensor with a plastic line rather than a conventional steel wire. The cable connector is also plastic (ie metal-free), which means the sensor can be used in applications where plant and equipment are sensitive to interference from conductive materials, or are installed in high-voltage environments where there must be no conductive connections between the sensor and target object.

The new P85 sensor with plastic line offers the same tensile strength, low thermal expansion properties and long service life as a conventional steel wire version. The plastic line also offers advantages to the end user in terms of reduced weight. Typical applications for the P85 with plastic line include medical X-ray machines, MRI scanners, dentist chairs and medical operating tables, where there must be little or no interference from measuring systems.

wireSENSOR mechanisms in the P85 series are designed to ensure simple mounting of an incremental or absolute encoder. The selection of the interface, resolution and type of connection can therefore be individually configured, which, in turn, provides optimum matching to the signal conditioning system. Mounting grooves on the four sides of the housing ensure simple, versatile installation.

Follow the link for more information about Micro-Epsilon's wireSENSOR series modular draw wire sensors.