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Gill Sensors was approached by a major UK manufacturer of domestic and industrial cleaning equipment requiring a low cost position sensor for incorporating into the accelerator pedal assembly of a ride-on scrubber dryer.
Due to their low price points, two of Gill Sensors’ products were considered – the Dual Cavity position sensor and the Blade25 position sensor. The Blade25 proved the best fit for the layout, space and measurement requirements, with the capability of being programmed for a wider range of conditions. Both linear measurements up to 25mm and angular measurements across 90 degrees easily covered the range of movement of the pedal.
The pedal position is determined by mounting a U-shaped metallic target, referred to as the activator, to the moving part of the pedal. This then passes over a series of coils mounted within the sensor. By alternately generating magnetic pulses in the coils and measuring differences in response from the activator, its position can be accurately determined.
One challenge that had to be addressed was the sensor detecting the surrounding material of the pedal itself, which was manufactured as a single pressed piece of mild steel. This problem was most evident when the pedal was against its open and closed bump stops, and was easily resolved by setting constant voltages beyond the upper and lower limits of the measurement range. These could be interpreted by the controller as ‘full on’ and ‘full off’ values. This had the added benefit of total inter-changeability between pedal assemblies, allowing the sensor to be standardised for production use.
With the calibration finalised, Gill has uploaded a serial data string into each of the sensors prior to dispatch removing any need for assembly line calibration. In addition, the Blade25 cable harness was customised for digital output, offering an RS-232 connector to allow seamless integration into the machine’s existing control unit. The adapted Blade25 sensors were then truly ‘plug and play’ and could to be built to order as need dictated.