Product category:
Proximity Sensors
News Release from: Variohm Eurosensor | Subject: TLI contactless position transducer
Edited by the Engineeringtalk Editorial
Team on 08 May 2001
Sensors upgrade 3-point linkages om farm
tractors
The TLI contactless position transducer from Novotechnik has recently been used by GKN Walterscheid to upgrade the three point linkage system on farm tractors.
The TLI contactless position transducer from Novotechnik GmbH has recently been used to upgrade the three point linkage system on farm tractors The traditional three point linkage system hasn't altered much since it was introduced in the 1920's
This article was originally published on Engineeringtalk on 30 Jun 2008 at 8.00am (UK)
Related stories
Industrial encoders for dummies
US manufacturer BEI has teamed up with the iconic "For dummies" brand to produce an innovative tutorial guide on industrial encoders.
Distribution deal covers load cell support
The Zemic loadcell range covers capacities from a few hundred grams to around 500 tons, with over fifty families of single-point, compression, S-type, shear beam and spoke-type load cells.
It forms the bridge between the tractor and the agricultural implement allowing some degree of positional adjustment whilst maintaining a constant operating force.
The exact setting of the linkage was always something of a compromise.
GKN Walterscheid have recently introduced a hydraulic top linkage arm which is designed to automatically optimise the position of the implement to suit the task being performed.
Further reading
Tiny draw-wire sensor suits long-term use
The M150 can be installed in a volume of less than 20 x 20 x 10mm and provides an essentially infinite linear position resolution over measurement range of 0 to 38mm
Angle sensor technology provides accuracy boost
Thin film deposits of sandwiched magnetic and nonmagnetic layers can be combined with sensors on 'spiral arms' to return an absolute position value over a single rotation.
The device utilises a linear position sensor which is integrated into the hydraulic cylinder which forms the body of the top linkage.
The operator uses a "Teach In" principle to find the best possible setting for the implement which he is using.
The system then remembers this setting and automatically adopts it whenever that particular implement is used.
In the GKN Waterscheid application the position sensor is a special non-contacting device with a stroke length of 250 mm, it sits directly in the hydraulic oil inside the cylinder.
This arrangement has a number of advantages the prime ones being that there are no additional projections around the cylinder, which can get damaged or take up space, and that the cylinder acts as a protective housing and keeps the sensor free from dirt, sand, water or any other environmental effects.
The sensor itself is an extremely clever device which employs a combination of resistive and capacitive technologies.
It utilises a conductive plastic resistance track like a conventional potentiometric transducer but in conjunction with a capacitive pickup rather than a conventional wiper.
Because it has no sliding contact the life expectancy is obviously much higher than a comparable potentiometric device.
In order for the capacitive pickup to work properly the resistance track has to be supplied from an alternating source which is obviously a problem on tractors.
The new sensor, designated the TLI, overcomes this problem by having an integral electronics package which converts the battery supply into an a.c.
source then evaluates the output from the capacitive pickup before returning it to a d.c.
output.
In effect the TLI is as easy to use as a conventional potentiometer.
Long term accuracy under even the most arduous conditions is guaranteed as the TLI offers a linearity of 0.15%, a resolution of 0.01 mm and a life expectancy of 200 million cycles.
It is available in stroke lengths of between 50 and 1000 mm.
Although this initial application is on a tractor the TLI is equally well suited to applications on any form of mobile hydraulic machinery.
• Variohm Eurosensor: contact details and other news
• Email this article to a colleague
• Register for the free Engineeringtalk email newsletter
• Engineeringtalk Home Page
Search the Pro-Talk network of sites
