NEXON EV SERVICE MANUAL

BRAKES 21 9.3. WHEEL SPEED SENSOR: (MONITORS WHEEL SPEED) Working principle: DF30 is an Active wheel speed sensor, which means it must be connected to a voltage source for operation. It supplies a signal with constant amplitude pulses whose frequency varies with the wheel speed. DF30 works on AMR principle (Anisotropic Magneto-Resistance) It has a semiconductor chip with the electronic circuitry for supply and signal processing integrated on it (Commonly known as ASIC – Application Specific Integrated Circuit) ASIC is mounted on Step Holder with magnetic circuit consisting of permanent magnet and sensing elements and then it is completely insulated/over moulded with Black Polyamide 612 GF33. DF30 wheel speed sensor is mounted directly above the magnetized encoder or steel tone wheel. The magnetized encoder/steel tone wheel is a ring with no’s of poles/teeth on it. Magnetized encoder or Tone wheel is fitted on to the bearing/wheel hub. The alternating poles/teeth and gap that accompanies the wheel rotation induces differential magnetic flux density, thus leading to the variation in the voltage induced in the ASIC. The signal conditioning circuit converts this voltage variation into constant amplitude current pulses. The frequency of these pulses depends up on the wheel speed. This measurement principle permits zero speed measurement. The distance between the sensor reading position surface and the target wheel surface is defined as the mechanical air gap (s_mechanic). It must be ensured that the lowest position of the encoder’s magnetic track/tone wheel tooth must be used as reference dimension for maximum air gap. To obtain correct signal, the specified gap between the end of sensor & the toner ring must be maintained according to project specific Air-Gap report shared by BOSCH during development. Example: Front: 0.5 mm to 1.5 mm Rear: 0.5 mm to 1.5 mm Precautions while handling DF30 Wheel Speed Sensor - Temperature specifications: Sensor head : (-40°C to +150°C) should not be exceeded Cable : (-40°C to +115°C) should not be exceeded Storage Life : From date of manufacture: 10 years under following conditions 1. Permitted temperature range: (-40 °C to +50 °C). Ambient humidity range: (5 up to 80 %RH). 2. The WSS is classified as an electrostatic discharge sensitive device (ESDS) requiring precautionary / protective measures in respect of handling and processing as defined in the corresponding internationally applicable standards (e.g. IEC 61340-5-1 series).Precise alignment and gap (1 mm) between the stator pole and the Toner wheel is vital. To obtain correct signal, the specified gap between the end of sensor & the toner ring must be maintained. Avoid any physical damage to DF30 Wheel Speed Sensor (e.g. Free fall, Sensor head scratched/cracked, exposed to strong magnetic field etc.) Repair of the product is not possible and not allowed. The sensor shall not be disassembled and reinstalled. Disassembly or repair may cause damage to the sensor and lead to a delayed malfunction of the sensor. Sensor failure like missing signal may lead to break down of safety related functions on system level. BOSCH warranty is excluded in case of reinstallation of disassembled sensors. Replacement of the product may only be performed by technically qualified personnel.