Product category:
Linear Position Sensors
News Release from: Penny + Giles | Subject: SLS190 position sensor
Edited by the Engineeringtalk Editorial
Team on 19 July 2000
Position sensors help load indicator
system
Penny and Giles Controls have provided a number of their latest SLS190 position sensors for use in an innovative load indicator system developed by industrial design engineer Dan Rees
Penny and Giles Controls have provided a number of their latest SLS190 position sensor for use in an innovative load indicator system that has been developed by Dan Rees, an industrial design engineer, who achieved a first class honours degree after studying at Brunel University in Egham, Surrey His 'LOAD' system is an axle load and weight distribution indicator for refuse collection vehicles
It targets a gap in a very competitive market by indicating axle loads rather than the gross vehicle weight offered by many other systems.
The system, which is competitively priced for fleet applications, prevents overloading by axle or gross vehicle weight.
This in turn prevents costly fines for both drivers and operators, increases operational safety and reduces road surface degradation due to overweight vehicles.
The rig used to develop the system is a scaled representation of a target vehicle - the Leyland DAF FA55 with a gross vehicle weight of 18 tonnes.
Its geometry has been calculated to produce representative deflection over the front and the rear axles and to take advantage of the 50mm electrical stroke of the Penny and Giles sensors.
Daniel says he approached Penny and Giles for the SLS190 linear position potentiometers because their specification was perfect for the application.
"They are sealable from the elements, robust, provide infinite resolution and are simply and cost-effectively connected to the microprocessor unit by shielded 3-way mini-DIN cables and connectors." He says.
The SLS190s are mounted to the vehicle on specifically designed aluminium brackets, which allow full movement of the sensors to prevent damage from road shock.
They also create a high integrity fixing for the required accuracy of the system.
The system's calibration procedure is believed to be unique in the commercial weighing market and is achieved in two ways.
Firstly, the fully loaded vehicle is weighed twice a year at an approved commercial vehicle weighbridge and, when the axle loads are known, trimming potentiometers are used to set the values recorded by the weighbridge.
Turning the trimming potentiometers maps the load to the sensor travel and vehicle spring rate.
The load distribution function, which displays the outputs of each of the sensors individually, can be used at this stage to equalise the output voltages from each pair of sensors.
Secondly, whenever the vehicle is empty the position of the sensors is reset to tare, a frequent resetting function effectively removing any error induced by road shocks.
The tare weight is used as a benchmark because it is the heaviest the vehicle can be whilst unloaded.
This provides a factor of safety against overload, as the vehicle is not usually at the maximum tare weight before being loaded.
The values from each sensor pair are compared to find the largest.
This value is the one considered for further interpretation and display, as it indicates the largest value that the axle load can take.
This is a failsafe system for protection against individual sensor defect or malfunction.
The load distribution function is useful to indicate the evenness of loading, as it displays the individual sensor values.
Uneven loads are indicated by the screen display.
This function is also used in the calibration to equalise the sensor output values per pair.
'LOAD' is now at the final development stage before production.
Dan Rees is confident that, with further support and investment, the project will result in the production of a commercially viable product that is simple to use, inexpensive, reliable and practical.
A spokesman for Penny and Giles says the company was pleased to be involved with a project that has proved to be such an innovative application for the SLS190 position sensor. Request a free brochure from Penny + Giles ...
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