Wireless Passive LC Temperature and Strain Dual-Parameter Sensor

Abstract

There is an increasing demand for bearing temperature and strain monitoring in high-speed rotating systems. This study proposes a new multiresonance, multiplexing, wireless, passive inductance capacitance (LC) temperature and strain sensor. The sensor has two capacitors connected at different locations (turns) on the same inductor to achieve simultaneous temperature and strain measurements. The plate capacitor is connected to the inner part of the inductor and the other interdigital capacitor is connected to the outer part of the inductor to form two LC loops. The structure of the sensor is optimized through High Frequency Structure Simulator (HFSS) simulations to realize frequency separation of the two parameters and avoid mutual interference between the two signals. The sensor is fabricated on a polyimide film using electroplating technology. The experimental results show that the temperature–strain sensor can operate stably from 25 °C to 85 °C with an average sensitivity of 27.3 kHz/°C within this temperature range. The sensor can detect strains in the range of 1000–5000 με with a strain sensitivity of 100 Hz/με at 25 °C. Therefore, the proposed wireless passive LC temperature-strain sensor exhibits stable performance. In addition, the use of a single inductor effectively reduces the sensor’s area. The flexible substrate provides advantageous surface conformal attachment characteristics suitable for monitoring high-temperature rotating parts in adverse environments.

Passive and Wireless All‐Textile Wearable Sensor System

“…These data confirmed the need to maintain a small vertical distance between the two inductors, as also observed in previous studies, where the vertical separation was restricted to 2 or 2.5 mm. [32,38] A misalignment in the inplane direction of up to half of the inductor size caused complete signal loss along the longer side of the rectangular planar inductor (Figure S7c, Supporting Information) but not on the short side (Figure S7d, Supporting Information). In-plane displacement of the two inductors seemed to have a higher impact on the frequency of the resonance peak as compared to the vertical displacement (Table S3, Supporting Information).…”

“…For wireless sensing with passive LC sensors, the external reader must be in close proximity to the inductor of the LC sensor. The resonance frequency shifts with these LC sensors have been previously recorded with a coupled inductor connected to benchtop vector network analyzers (VNA), [5,31,34,35,38] or impedance analyzers. [39] These readers are not suitable for wearable applications due to their bulky nature (even downsized VNAs) and cannot be integrated into daily living.…”

Wheel-Rail Force Measurement Based on Wireless LC Resonance Sensing

“…Like ECT performing at the electrical resonance, inductor-capacitor (LC) wireless passive sensors are also based on the measurement in the shift of the resonant frequency. They have been successfully utilized on strain measurement [23][24][25][26][27]. An LC sensor consists of an inductor coil and a sensing capacitance where the capacitance changes in response to parameters of interest, with a shift in its resonant frequency [23].…”

“…An additional readout coil connected to a vector network analyser (VNA) can be used to interrogate LC sensors and detect the frequency shift by monitoring the impedance change and return loss of the readout coil [23]. Most research on LC sensors concentrates on the design of sensing capacitors using advanced materials such as polymer, graphene, multiwalled carbon nanotubes (MWCNs), nanocomposite, and polydimethylsiloxane (PDMS) [26], [28], [29]. The induction coil in those studies only plays a signal transmission role rather than sensing.…”