Direct interface for capacitive sensors based on the charge transfer method

Gaitan-Pitre, J.E.; Gasulla, Manel; Pallás-Areny, R.

doi:10.1109/imtc.2007.379227

Cited by 10 publications

(5 citation statements)

References 5 publications

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“…A slight modification of the method proposed in [25] is shown in [28], where one more cycle of measurement is used to obtain errors of less than 2% for C X in the range 100 pF -2.2 nF. X can be found using [29] ( )…”

Section: State Of the Artmentioning

confidence: 99%

“…where N X , N C1, and N C2 are the number of charge transfer cycles needed for C X , C C1, and C C2, respectively. This method can obtain maximum errors of 0.8% FSR for the range 100 pF -1 nF [32], but, unfortunately, calibration processes are also needed (in [33], an application of the methods proposed in [29]- [32] to detect urine leakage is shown).…”

Section: State Of the Artmentioning

confidence: 99%

“…In this method, C X , C C1, or C C2 are charged with a logical 1, and the charge is transferred to C Ref , initially discharged, also fulfilling C Ref >> C X , C C1, and C C2 . By measuring the number of charge transfer cycles it takes for the voltage stored in C Ref to reach V TH (V TH is the threshold voltage to detect a logical 1 input starting from a logical 0 level), CX can be found using[29]…”

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confidence: 99%

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Simplifying Capacitive Sensor Readout Using a New Direct Interface Circuit

Hidalgo-López

Castellanos-Ramos

2023

IEEE Trans. Instrum. Meas.

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Direct interface circuits (DICs) are efficient for reading resistive, capacitive, or inductive sensors in digital format. The simplest DICs consist of just a few passive elements that connect a digital processor (DP) to a sensor. When reading capacitive sensors, one or several calibration capacitors and/or several charging and discharging cycles are needed to make the estimation, and the result usually requires complex arithmetic operations. This article presents a new type of capacitive DIC that is simple in terms of hardware, needing only two resistors of known value and the DP in order to make the capacitance estimation. In addition, the reading method requires a single sensor charging and discharging cycle, which reduces acquisition time and power consumption. Two time measurements are taken during the discharge which, through a linear transformation of their subtraction (using two constants stored in the DP), give the value of the capacitance. These arithmetic operations are easily implemented on any DP and consume fewer resources than the divisions required on other capacitive DICs. The design has been tested for a wide range of capacitances (from 100 pF to 561 nF), including the value of several capacitive sensors. The average relative error for the entire range is 0.41%, linearity errors are below 0.3%, and the minimum signal-to-noise ratio value is 64 dB.

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Section: State Of the Artmentioning

confidence: 99%

Section: State Of the Artmentioning

confidence: 99%

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confidence: 99%

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Simplifying Capacitive Sensor Readout Using a New Direct Interface Circuit

Hidalgo-López

Castellanos-Ramos

2023

IEEE Trans. Instrum. Meas.

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“…Direct interface circuits (DICs) [5] are a series of circuits based on methods that use a small number of additional components to make the connection between a sensor and a programmable digital device (PDD). There are DICs for resistive sensors [6,7,8,9,10,11,12,13,14], capacitive [15,16,17] or inductive [18,19,20,21,22] sensors, and even DICs built to measure any of them [23].…”

Section: Introductionmentioning

confidence: 99%

Quasi Single Point Calibration Method for High-Speed Measurements of Resistive Sensors

et al. 2019

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Direct interface circuits are a simple, inexpensive alternative for the digital conversion of a sensor reading, and in some of these circuits only passive calibration elements are required in order to carry out this conversion. In the case of resistive sensors, the most accurate methods of calibration, namely two-point calibration method (TPCM) and fast calibration methods I and II (FCMs I and II), require two calibration resistors to estimate the value of a sensor. However, although FCMs I and II considerably reduce the time necessary to estimate the value of the sensor, this may still be excessive in certain applications, such as when making repetitive readings of a sensor or readings of a large series of sensors. For these situations, this paper proposes a series of calibration methods that decrease the mean estimation time. Some of the proposed methods (quasi single-point calibration methods) are based on the TPCM, while others (fast quasi single-point calibration methods) make the most of the advantages of FCM. In general, the proposed methods significantly reduce estimation times in exchange for a small increase in errors. To validate the proposal, a circuit with a Xilinx XC3S50AN-4TQG144C FPGA has been designed and resistors in the range (267.56 Ω, 7464.5 Ω) have been measured. For 20 repetitive measurements, the proposed methods achieve time reductions of up to 61% with a relative error increase of only 0.1%.

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“…With respect to the integration of capacitive sensors in electronic circuits, there are many different circuits' configurations to measure capacitance. Among the alternatives, one of the most used is the charge transfer [11] and the current sense amplifier [12]. Another one is based on an alternating current bridge [13].…”

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confidence: 99%

Recent Advances in Printed Capacitive Sensors

Rivadeneyra

López‐Villanueva

2020

Micromachines

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In this review paper, we summarize the latest advances in the field of capacitive sensors fabricated by printing techniques. We first explain the main technologies used in printed electronics, pointing out their features and uses, and discuss their advantages and drawbacks. Then, we review the main types of capacitive sensors manufactured with different materials and techniques from physical to chemical detection, detailing the main substrates and additives utilized, as well as the measured ranges. The paper concludes with a short notice on status and perspectives in the field.

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Direct interface for capacitive sensors based on the charge transfer method

Cited by 10 publications

References 5 publications

Simplifying Capacitive Sensor Readout Using a New Direct Interface Circuit

Simplifying Capacitive Sensor Readout Using a New Direct Interface Circuit

Quasi Single Point Calibration Method for High-Speed Measurements of Resistive Sensors

Recent Advances in Printed Capacitive Sensors

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