A motorsports braking application sensor was experiencing failures due to the extreme temperatures at the tip of the sensor when brakes were applied. Temperatures were in excess of 232C. Sensor installation required the attachment of cabling with an immediate 90 degree angle at the end of the sensor and the ability to provide flexible routing on the car chassis.
Solution – High Temperature Variable Reluctance Sensor
While a standard high temperature variable reluctance sensor would provide sufficient operating temperature (up to 850F continuous and 1000F intermittent), standard construction calls for a #24 AWG thermocouple lead that is more rigid than a Teflon cable and a ceramic potting that would have difficulty withstanding the rugged environment underneath the car. Testing by the customer indicated that other than at the tip end of the sensor, temperatures did not exceed 220C, allowing for a hybrid sensor design using components suited for varied temperatures and high temperature internals for the winding to withstand the elevated temperatures at the sensor tip and a lower temperature Teflon cable/epoxy solution at the back end to provide the ruggedness and flexibility required by the application.