An &lt;italic&gt;LC&lt;/italic&gt;-Type Passive Wireless Humidity Sensor System With Portable Telemetry Unit

Zhang, Cong; Wang, Lifeng; Huang, Jianqiu; Huang, Qing‐An

doi:10.1109/jmems.2014.2333747

Cited by 58 publications

(34 citation statements)

References 23 publications

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“…The readout circuits to capacitive RH sensors can be classified as capacitance-to-voltage (C2V) [14], capacitanceto-frequency (C2F) [15] and capacitance-to-time (C2T) transducers [16], all of which are based on charging and discharging CRH. To reject the large common-mode signal (see Fig.…”

Section: B Existing Readout Circuits To Capacitive Sensorsmentioning

confidence: 99%

A Capacitance-to-Digits Readout Circuit for Integrated Humidity Sensors for Monitoring the In-Package Humidity of Ultra-Small Medical Implants

Wen

Demosthenous

Donaldson

et al. 2018

2018 IEEE International Symposium on Circuits and Systems (ISCAS)

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Integrated humidity sensors, especially the capacitive type, are increasingly used for implanted electronic devices for assessing the hermeticity of implant packages and monitoring the in-package environment in which delicate electronics are operating. We have developed a simple capacitance-to-digits readout circuit for a capacitive humidity sensor that is used for monitoring the in-package humidity of ultra-small medical implants. The proposed readout circuit provides a larger dynamic range than conventional capacitance readout circuits by removing the parasitic capacitance from the measured capacitive input. Its simple circuit structure and lowpower consumption make it suitable for implant applications.

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Section: B Existing Readout Circuits To Capacitive Sensorsmentioning

confidence: 99%

A Capacitance-to-Digits Readout Circuit for Integrated Humidity Sensors for Monitoring the In-Package Humidity of Ultra-Small Medical Implants

Wen

Demosthenous

Donaldson

et al. 2018

2018 IEEE International Symposium on Circuits and Systems (ISCAS)

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“…This solution exploits the magnetic coupling between a primary and a secondary coil to read passive sensors. The primary coil, along with the reading circuitry, forms the readout unit, which reads the sensor unit composed of the sensor element connected to the secondary coil [ 14 , 15 , 16 , 17 ]. This approach offers the promising advantage of reducing the cost of the passive sensor unit, allowing the production of disposable sensors, such as labels, with a passive sensor connected to the embedded coil [ 18 , 19 ].…”

Section: Introductionmentioning

confidence: 99%

Interrogation Techniques and Interface Circuits for Coil-Coupled Passive Sensors

et al. 2018

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Coil-coupled passive sensors can be interrogated without contact, exploiting the magnetic coupling between two coils forming a telemetric proximity link. A primary coil connected to the interface circuit forms the readout unit, while a passive sensor connected to a secondary coil forms the sensor unit. This work is focused on the interrogation of sensor units based on resonance, denoted as resonant sensor units, in which the readout signals are the resonant frequency and, possibly, the quality factor. Specifically, capacitive and electromechanical piezoelectric resonator sensor units are considered. Two interrogation techniques, namely a frequency-domain technique and a time-domain technique, have been analyzed, that are theoretically independent of the coupling between the coils which, in turn, ensure that the sensor readings are not affected by the interrogation distance. However, it is shown that the unavoidable parasitic capacitance in parallel to the readout coil introduces, for both techniques, an undesired dependence of the readings on the interrogation distance. This effect is especially marked for capacitance sensor units. A compensation circuit is innovatively proposed to counteract the effects of the parasitic input capacitance, and advantageously obtain distance-independent readings in real operating conditions. Experimental tests on a coil-coupled capacitance sensor with resonance at 5.45 MHz have shown a deviation within 1.5 kHz, i.e., 300 ppm, for interrogation distances of up to 18 mm. For the same distance range, with a coil-coupled quartz crystal resonator with a mechanical resonant frequency of 4.432 MHz, variations of less than 1.8 Hz, i.e., 0.5 ppm, have been obtained.

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“…Besides sensing applications for pressure, position, proximity, liquid level measurement and material analysis, capacitive techniques are promising for contactless operation. Passive wireless humidity sensors [1] and non-contact passive electromagnetic interfaces especially dedicated to capacitive sensors [2][3][4] have been demonstrated, but these adopted measurement techniques generally suffer from a dependency on the interrogation distance, which makes them difficult to apply in real operating conditions. Differently, this paper presents a contactless interrogation system for capacitive sensors that exploits a specific time-gated technique firstly developed for piezoelectric resonant sensors [5,6].…”

Section: Introductionmentioning

confidence: 99%

Contactless Interrogation System for Capacitive Sensors with Time-Gated Technique

Masud

Baù

Demori

et al. 2017

Proceedings of Eurosensors 2017, Paris, France, 3–6 September 2017

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This paper presents a measurement technique and system for the contactless interrogation of capacitive sensors via electromagnetic coupling. The interrogation unit employs a primary coil to periodically excite the capacitive sensor connected to a secondary coil forming an LC resonant circuit. When the excitation to the primary coil is switched off the damped response of the LC circuit is detected. As a fundamental advantage compared to techniques based on reflected impedance, this approach ensures that the readout frequency is to first order independent of the interrogation distance between the two coils. The system has been tested with reference capacitors and with a capacitive liquid level sensor. The experimental results are in a good agreement with theoretical expectations and show a sensitivity of about −23 kHz/pF at 5.4 MHz and the possibility to operate with interrogation distances up to few centimeters.

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An <italic>LC</italic>-Type Passive Wireless Humidity Sensor System With Portable Telemetry Unit

Cited by 58 publications

References 23 publications

A Capacitance-to-Digits Readout Circuit for Integrated Humidity Sensors for Monitoring the In-Package Humidity of Ultra-Small Medical Implants

A Capacitance-to-Digits Readout Circuit for Integrated Humidity Sensors for Monitoring the In-Package Humidity of Ultra-Small Medical Implants

Interrogation Techniques and Interface Circuits for Coil-Coupled Passive Sensors

Contactless Interrogation System for Capacitive Sensors with Time-Gated Technique

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