Signal conditioning


The sensor inside a conveyor belt


Elegant engineering is all around us. The Face ID in your phone, the keyless go in your car, the smart speaker in your home; these devices make our lives perceptibly easier. What is not always easy are the novel design challenges engineers must overcome to realise these products. When Habasit, a leading provider of conveyor and power transmission systems, hatched an ambitious plan to create an embedded wireless force-sensing link in one of its curved plastic modular belt conveyor systems, it worked with Mantracourt to achieve elegance.


manufacturer of conveyor and power transmission systems, based in Reinach, Switzerland. A large customer in the food and beverage industry had recently come to Habasit with a query; it wanted to measure tension in the spiral conveyor belt system on its bread production line. After the bread came out of the oven, it


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made its way through the rising spiral conveyors to allow it to cool before being packaged. Reminiscent of the holding pattern sometimes used by passenger aircraft on the approach to an airport, the spiral conveyors are a common sight in many food production environments. They offer a space saving way of increasing production throughput and are also used to move products up and down between different levels in the plant, sometimes reaching a height of two storeys. However, because the belt in a spiral


conveyor needs to follow a curved path, as well as a straight path, one of the biggest challenges these types of conveyors face is tension. High levels of tension in the belt can cause it to buckle and/or break. In the food industry in particular, this problem is


exacerbated by food particles from the likes of bread and pastries becoming lodged in the gaps


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n 2018, Andrew Richardson was working as a project manager in the plastics R&D department at Habasit, a leading global


between the plastic links. Between cleaning cycles, this leads to an increase in friction, which leads to higher belt tension. “In the industry today, it’s common for


engineers to measure the condition of motors and pumps,” explains Richardson. “However, it’s less common to measure the force inside the conveyor belt itself. It’s a very challenging environment, with ovens and chillers working in close proximity to make everything from frozen pizza to cooked chicken.” Using sensors in this environment is not easy.


The traditional approach involves a maintenance engineer visiting the site to carry out repairs and upgrades. During these visits, the engineer will also check tension using a load-cell that clips onto the surface of the belt and measures the force between the modular links. However, this approach has its limitations. “The downside with this method is that it only


takes place periodically as part of the scheduled maintenance visits and means stopping the conveyor,” explains Richardson. “Secondly, the load cell that measures tension only works on some parts of the conveyor system and can’t fit through tight spaces, so you only really get a limited picture of belt tension in the system.” The team at Habasit came up with an ambitious


plan to create a sensor that would fit inside a metal link that was the same shape and size as one of the existing plastic modular links in the belt. This


special link would continuously transmit data wirelessly back to a base station. “We knew it was not an easy design


engineering challenge,” says Richardson. “All of the electronics had to fit inside the small envelope occupied by the link, including the sensor, the circuit board, the battery and the antenna. The components had to be durable enough to withstand extreme temperature changes and the wireless transmission had to reliably relay data through the complex plant environment.” Habasit reached out to partner with a


specialist to support the development of the link, but initially struggled. “The relationship with the first company we engaged with quickly fell through due to a lack of responsiveness,” says Richardson. “We then reached out to Mantracourt and hit it off immediately. This was before the pandemic, so our team flew out to the UK and spent the day with the team at Mantracourt, to really give them a feel for our needs.” Mantracourt designs and manufactures signal


conditioning equipment and sensor systems, specialising in miniature high-performance electronics and wireless telemetry systems. “The link is made up of four areas,” explains


Tom Lilly, application engineer at Mantracourt. “At the most basic level, a strain gauge sensor connected to the internal frame of the metal link


August 2021 Instrumentation Monthly


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