Wireless temperature sensing using temperature-sensitive dielectrics within responding electric fields of open-circuit sensors having no electrical connections

Abstract

All temperature sensors or sensor systems previously developed have one common feature-–the sensors are part of electrically closed circuits and electrical connections are used to form the closed circuits. Using existing frameworks for designing, powering and interrogating sensors, any damage that ruptures the circuit can render the sensor non-functional. In many damage events, it is necessary to identify that the damage has occurred and also continue the measurement. In this paper we report a new temperature sensing method that uses a recently developed technique for designing, powering and interrogating sensors developed at NASA. In lieu of sensors being a collection of components assembled using electrical connections, the open-circuit sensors are patterns of electrically conductive material that can store electric fields and magnetic fields without electrical connections. These sensors are powered using oscillating magnetic fields and respond with their own electric and magnetic fields whose signatures provide temperature information. Because no electrical connections are used, there is no point on the sensor that if damaged renders the sensor non-functional. Damage to the sensor simply shifts the sensor's frequency range, allowing it to continue measurement while damaged. Temperature-sensitive dielectric material is placed within the sensor's responding electric field to modulate the sensor's resonant frequency. Temperature sensitivity and functional temperature range are dependent upon the temperature-sensitive material used and how it is placed within sensor's responding electric field. The principle and design strategies of the open-circuit temperature sensors are discussed and experimental results are presented.