Long travel linear position measurement

Variohm supply draw wire sensors to Hunger Hydraulics for lifting bridge application

Towcester – UK – November 2015: Hunger Hydraulic UK Ltd, a part of the international Hunger Hydraulic system consultancy and solutions group, has recently supplied four 4.25 metre stroke telescopic hydraulic cylinders to main contractor John Sisk, to lift a new 80-metre pedestrian and cycle access bridge linking Canning Town station to a new island development on the Leamouth Peninsula in London.

The 160 tonne bridge which was successfully commissioned in July 2015, is raised vertically to allow boats to navigate the river and as an integral part of its hydraulic control and synchronisation system, includes four Celesco SR1 series draw wire linear position sensors that were specified and supplied by Celesco’s UK distributor Variohm EuroSensor.

As conventional hydraulic linear position sensor types could not be considered due to the telescopic style long travel cylinders, Hunger designers opted for draw wire or cable sensor technology and chose the competitively priced Celesco SR1 for its well proven reputation in outdoor construction, agricultural and industrial equipment for rugged build quality and extended durability.  For redundancy purposes, two sensors are mounted and work in parallel each side of the bridge. To ensure complete protection the sensor pairs are encased in a pivoting steel housing which includes telescopically extended cylindrical sections that fully enclose the cable.

For this application, the SR1M model draw wire sensor provides a user-scalable 4…20 mA proportional signal to the control system. The sensor is supplied factory calibrated to the full stroke range but thanks to its internal programmable digital circuitry the output signal can be easily re-scaled to match the actual application stroke length with an easy-to-use push-button zero and span adjust.

Other models in the SR1 series include voltage divider, 0-5/0-10 VDC and incremental encoder versions with standard stroke lengths of 3175 and 4445 mm. The plastic-hybrid precision potentiometer returns a rated life of 250,000 cycles with positional accuracy specified at 0.5% FS with repeatability to 0.1% FS. Along with many draw wire sensors from Celesco Inc., the SR1 is designed for outdoor use featuring an IP67 environmental rating, tough polycarbonate housing and a nylon coated stainless steel cable. The sensor can be universally mounted with cable exit positions oriented in up, down, rear and forward directions and no critical alignment is required. Electrical connection is via an M12 connector with mating cable-sets available.

Variohm EuroSensor is a designer, manufacturer, distributor and supply chain partner providing complete sales and application support across a comprehensive range of position, load, force and temperature sensor technologies - for demanding measurement applications across industry, construction, agriculture, motorsports, research and more.