Coupled Resonant Coil Sensors for Remote Passive Monitoring Applications
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The thesis describes development and application of coupled resonant coil sensors, which is of growing interest for remote monitoring applications. An interrogation technique, which improves the accuracy and interrogation range of coupled resonant coil sensors, is introduced. The method uses time-domain gating to produce measurements that are dominated by the response of the sensor coil and are immune to surrounding object interference. For application in structural health monitoring a low cost embeddable coupled coil sensor, which is able to monitor the corrosion potential of reinforcement steel is presented. Results of an accelerated corrosion test using the sensor indicate that corrosion potential can be monitored with a resolution less than 10 mV and a sensitivity of 0.76 kHz/mV. The last part describes a coupled-coil pH sensor based on pH electrode potential measurement. A linear response over a 4 to 10 pH dynamic range and 50 kHz/pH sensitivity are achieved with a 0.1 pH resolution and 30 s response time.