Abstract

Inductive proximity sensors are widely used in the aerospace industry for non-contact metal sensing. The main advantages are that they can operate in a harsh environment, providing a rapid response time and a long operational life. To overcome the problem of temperature drift, this thesis presents a novel excitation method that automatically compensates the temperature variations as well as providing precise distance outputs. The inductance and resistance values of the sensor are measured separately. These values can be used to determine the proximity distance and the temperature of the sensor independently. By having this methodology, a Field-Programmable Gate Array (FPGA) design is implemented using look-up tables and DSP (Digital Signal Processing) blocks to accurately measure the proximity distance based on the measured inductance value. Our experimental data shows that we are able to measure the distance in the range of 0 – 5 mm with less than 2% error in the temperature range of -30 °C and +70 °C. Moreover, this method is scaled to support multiple sensors with different internal characteristics up to 10 sensors using a single processing circuit. This is a major improvement over existing electronic circuits which are limited to one sensor type. Finally, an automated test platform is designed to accelerate the test and development process.