E-Mobility Engineering 015 l EMotive Scarab off-road truck dossier l In Conversation: Giulio Ornella l Hall effect and magnetic sensors focus l Challenge of batteries for heavy-duty EVs l Alpha Motor Corporation digest l Automated charging insight l HVAC systems focus

12.7 mm. Reading the sensors in 800 ms provides an image of the magnetic field’s distribution. Every sensor measures the local magnetic field, and the distribution allows many properties of the magnets to be derived. The camera array uses basic physics inherent in the field to calculate the overall magnetic field around the magnet. That means the field at a particular distance, for example 2 mm from a magnet, can provide the data for distances at 0.5 mm and 5 mm without having to move. The algorithms in the camera’s control software are computationally correct and are based on the Maxwell equations to give the depth, or Z, data. These algorithms give the Z data for the entire field from a single point, given that the field can be measured as the boundary condition. that it could measure fields 100 times smaller than devices using silicon plates. The size of the graphene sheet is also variable, allowing very small devices to be made. The active area can be from 10 to 100 µm 2 , and the size is determined more by the space for the contact pads. This opens up the opportunity to put thousands of sensors on a chip to create a magnetic field camera. The 2D nature of the graphene plate also avoids any crosstalk between the sensors in the array. The smaller sensors are being used to pick up more of the current flowing through a cell, opening up a new area for characterising a pouch battery cell. Sensors can be placed on the top and bottom of the pouch cell to detect the size and direction of the different current flows in the various layers of the cell. This mechanism is not well- understood, but the measurements will help to characterise the cell performance, giving more information that can lead to improvements in the lifetime and safety of a cell’s construction. Graphene Hall effect sensors are also being tested in fast charging systems with hundreds of amps to provide an instantaneous read-out of current alongside a PT100 temperature sensor, as the performance of the sensor is temperature-dependent. Hall effect array Hall effect sensors are also used in a massive array to create a magnetic field camera for inspecting equipment in the quality control of permanent magnet assemblies. A chip, built in a silicon process, has a 128 x 128 array of sensors on a 0.1 mm pitch to give a matrix of 16,384 sensors; the chip measures 12.7 x Wire bonding a graphene Hall effect die onto its package (Courtesy of Paragraf) 38 Autumn 2022 | E-Mobility Engineering