Sensor applications in agricultural machinery

Variohm EuroSensor has successfully undertaken a number of applications with UK and European farm machinery manufacturers for position, load, pressure and temperature sensors with almost all of them installed in harsh outdoor environments where large temperature extremes as well as severe shock and vibration conditions exist - and upmost reliability is essential. Applications range from angle sensors in sophisticated four-wheel steering systems that allow farm machinery to precisely manoeuvre in tight spaces for maximum crop yields to linear position and load sensors that are part of advanced mobile autonomous vehicles linked to the Global Navigation Satellite System (GNSS) for vehicle guidance and load weight measurement.

These various types of sensors serve numerous measurement tasks. Some are configured open loop with the position or load information simply fed to a visual display to allow manual operation of a process. Other automated and autonomous machine tasks involve the sensing component as part of closed loop systems where often multiple functions are synchronised, for instance with vision systems and linear motion positioners or rotary actuators for tasks such as in-row weeding or selective crop harvesting.

The high precision angle and linear position sensing technologies offered by Variohm include potentiometric based sensors where there is a physical contact between a conductive plastic track and wiper contact in a housed assembly. As the sensor is extended or rotated, the position information is provided as a linearly proportional voltage measurement.

For rotary angle sensing, Variohm offers two Hall Effect technologies where there is no contact between a fixed sensing element and a rotating magnet. Whilst these sensor types do not differ in the actual way the sensing takes place, they can be differentiated by the first ‘non-contacting’ type having an enclosed and housed assembly complete with bearings (so there is a degree of contact involved) - and a second type of ‘touchless’ sensor where the sensor and magnet are supplied as separate components and mounted by the customer between the fixed and rotating components. Variohm manufactures a range of Hall Effect angle sensors that are well suited to agricultural applications.

Three mechanical design formats with encapsulated sensor electronics form the Euro-XP, XPD and XPK series. The XP and XPD are durable, housed versions featuring optional ‘U’ or ‘Spring’ shaft drives and a D-shaft drive respectively, both with flange mounting and integral bearings. The third version, the Euro XPK, is a two-part ‘puck and magnet’ contactless design. Variohm’s comprehensive range of angle sensors also covers non-contacting sensor technologies with multi-turn capability so that, if attached to ballscrew or leadscrews for instance, they can be calibrated to measure travel length.