Wireless measurement technique for telemetry low-value resistive sensors

The measurement of different quantities in harsh environments, such as those at high temperatures and/or in hermetic environments, presents considerable difficulties due to various factors, including the characteristics of the harsh environment itself, which do not allow the proper use of the electronics and / or using connection cables between the harsh and the safe environment. An adoptable solution is given by passive telemetry systems that include a passive sensor placed inside the harsh environment. Non-contact techniques are adopted to read the quantities. The measurement technique that is proposed may be adopted for resistive sensors. The system consists of a resistive sensor that is connected to an inductor and coupled to a second inductor positioned externally. The external inductor is connected to the readout electronics and permit, using the proposed technique, to calculate the value of the sensor resistance. The adopted telemetric technique is based on a measurement of the impedance at the terminals of the readout inductor and on a mathematical elaboration to extract the sensor resistance. The circuit model of the telemetric system is presented, several consideration on the telemetric technique are reported based on simulations and experimental results.