An improved capacitance pressure sensor with a novel electrode design

Lower limb prosthetic socket fabrication is a highly refined process relying on the prosthetist's skill and experience. Despite their best efforts, patients often return with complications. Additionally, clinical application of technological advances for the quantification of biomechanical factors at the socket interface has not changed in practice. Measuring pressure levels at the stump/socket interface could provide valuable information in the process of prosthetic socket fabrication, fit and modification.This paper presents findings on the performance of a prototype capacitance pressure sensor designed for prosthetic socket use. Bench tests using compressed air were performed to measure accuracy, hysteresis and drift responses in both a flatbed chamber and a custom-modified pressure vessel. For the contoured testing, the sensors were placed on nine sites on a positive trans-tibial stump mould and enveloped with a silicone liner. Additionally, a preliminary clinical evaluation was performed with two trans-tibial amputee subjects at the nine sites during normal ambulation.Bench test results showed that the prototype capacitance sensor performed well in all categories, exhibiting a 2.42% (flatbed) and 9.96% (contoured) accuracy error, a 12.93% (flatbed) and 12.95% (contoured) hysteresis error, and a 4.40% (flatbed) and 6.20% (contoured) drift error. The clinical study showed that after three hours of continual use, no noticeable sensor drift occurred between pre and post-test calibration values.The results from this study were encouraging and the authors hope to conduct further laboratory and clinical trials to assess the influence of shear force and dynamic loading on sensor response.

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A Thin-Film Capacitance Pressure Sensor

Measurement Techniques ◽

10.1007/s11018-015-0641-2 ◽

2015 ◽

Vol 57 (12) ◽

pp. 1403-1410 ◽

Cited By ~ 1

Author(s):

A. A. Kazaryan ◽

E. V. Strel’tsov

Keyword(s):

Thin Film ◽

Pressure Sensor ◽

Capacitance Pressure

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Linearization of Characteristic Response of a Capacitive MEMS Pressure Sensor by Patterning the Dielectric Layer

Volume 1: 14th International Conference on Micro- and Nanosystems (MNS) ◽

10.1115/detc2020-22210 ◽

2020 ◽

Author(s):

Nadia Ebrahimpour Tolouei ◽

Mohammad Shavezipur

Keyword(s):

Pressure Sensor ◽

Dielectric Layer ◽

Contact Region ◽

Quantitative Measure ◽

Capacitive Pressure Sensor ◽

Contact Mode ◽

Insulating Layer ◽

Capacitance Pressure ◽

Capacitive Mems ◽

Novel Design

Abstract The present work introduces a novel design that linearizes the characteristic capacitance-pressure (C-P) response of the pressure sensor in contact mode. The design relies on patterning the insulating (dielectric) layer that separates the two electrodes of the device when the device is in contact mode. Since the capacitance is inversely proportional to the gap between the electrodes and the dielectric constant of the insulating layer is several times more than that of air (or vacuum), the contact region of the two electrodes makes more significant contribution to the overall capacitance of the system. Therefore, if the dielectric layer is properly patterned, the shape of C-P response can be controlled. In this work, we focus on linearity of the sensor response, and design and optimize dielectric pattern to achieve the highest linearity. Finite element simulations are used to demonstrate the applicability of the design concept. Different sensor designs are modeled and simulated using ANSYS® Multiphysics solver and their responses are compared to that of a conventional capacitive pressure sensor. Coefficient of linear correlation between pressure and capacitance is used as a quantitative measure for improvement of linearity. The simulation results show that the linearity of the C-P response improves from 0.930 in a 600 μm-diameter conventional design to 0.978 for a sensor with patterned dielectric layer. Moreover, a smaller sensor with 300 μm diameter display linearity of 0.999 over a 1.25 MPa – 5.0 MPa pressure range.

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Capacitance pressure sensor with S-type electrode for improved sensitivity

Transactions of the Institute of Measurement and Control ◽

10.1177/01423312211008001 ◽

2021 ◽

pp. 014233122110080

Author(s):

Santhosh KV ◽

Swetha Rao

Keyword(s):

Pressure Sensor ◽

Pressure Sensors ◽

Differential Pressure ◽

Capacitive Pressure Sensor ◽

Input Output ◽

Capacitance Pressure ◽

Output Behavior ◽

Output Characteristics ◽

Differential Pressure Sensor ◽

Output Capacitance

This paper aims at designing a differential pressure sensor. The objective of the work is to design and fabricate the electrodes of a capacitive pressure sensor, so as to measure absolute and differential pressure accurately with improved sensitivity. In place of conventional parallel plate diaphragm, S-type electrodes are proposed in the present work. The work comprises of study of the proposed design in terms of a mathematical model, input-output behavior along with detailed analysis of pressure distribution pattern. Output capacitance obtained for changes in pressure is converted to voltage with the suitable signal conditioning circuit and data acquisition system to acquire the signal on to a PC. A neural network model is designed to compensate the nonlinearities present in the sensor output. Input-output characteristics of the designed sensor shows an improved response as compared with existing pressure sensors.

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A low hydraulic capacitance pressure sensor for integration with a micro viscosity detector

Sensors and Actuators B Chemical ◽

10.1016/s0925-4005(03)00099-6 ◽

2003 ◽

Vol 92 (1-2) ◽

pp. 102-109 ◽

Cited By ~ 5

Author(s):

F.H.J. van der Heyden ◽

M.T. Blom ◽

J.G.E. Gardeniers ◽

E. Chmela ◽

M. Elwenspoek ◽

...

Keyword(s):

Pressure Sensor ◽

Hydraulic Capacitance ◽

Capacitance Pressure

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A Capacitive MEMS Pressure Sensor With Wavy Membrane and Linear Capacitance-Pressure Response

Volume 4: 24th Design for Manufacturing and the Life Cycle Conference; 13th International Conference on Micro- and Nanosystems ◽

10.1115/detc2019-98021 ◽

2019 ◽

Author(s):

Stephen Oke ◽

Mohammad Shavezipur

Keyword(s):

Pressure Sensor ◽

Ambient Pressure ◽

Pressure Sensors ◽

Wave Form ◽

Capacitive Pressure Sensor ◽

Working Pressure ◽

Sensing Applications ◽

Wide Range ◽

Capacitance Pressure ◽

Capacitive Mems

Abstract A novel structure for capacitive MEMS pressure sensors is presented that can be used for a wide range of pressure sensing applications. The sensor is designed such that its characteristic capacitance-pressure (C-P) response is highly linear and could cover a wide range of working pressure. A capacitive pressure sensor includes two capacitive electrodes, one patterned on the substrate and the other one suspended creating a sealed cavity. The suspended electrode acts as the pressure sensitive membrane in the device and undergoes out-of-plane deformation when there is a change in ambient pressure, resulting in a change in the device’s capacitance. The design presented in this work uses a wavy-shape membrane with controlled deformations to provide a highly linear C-P response. The wavy shape of the membrane can be fabricated using grey-scale mask and lithography. ANSYS APDL multiphysics solver is used to model and simulate the pressure sensor and optimize its response. The material used in the design and simulations of the pressure sensor is silicon carbide making this design suitable for harsh environment applications. The simulation results show that if the size and the shape of the wave form in the membrane are optimized, highly linear C-P response can be achieved and also its working pressure range can be extended.

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