Simple and robust microcontroller-based acquisition system for differential capacitive sensors

Depari, A.; Sisinni, Emiliano; Bellagente, Paolo; Ferrari, Paolo; Flammini, A.; Rinaldi, Stefano

doi:10.1109/i2mtc50364.2021.9460034

Cited by 4 publications

(11 citation statements)

References 26 publications

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“…Some DICs measure purely resistive sensors [1], [2], [3], purely capacitive sensors [4], [5], and purely inductive sensors [6]. We can also find DICs for reading differential resistive sensors [7], [8], differential capacitive sensors [9], [10], or differential inductive sensors [11], as well as DICs, to read lossy capacitive sensors that present a parasitic shunt resistor with the capacitive sensing element [12], [13]. In symmetrical situations, with a resistive sensor affected by a parasitic parallel capacitance, we can use, for example, the DIC proposed in [14].…”

Section: Introductionmentioning

confidence: 91%

“…There are a variety of sources of error in the estimate provided by (9). First, one must consider the parasitic capacitors that appear in the implementation of the circuit.…”

Section: B Error Analysismentioning

confidence: 99%

“…However, while C In and C m can slightly slow down the charging of C X , they do not affect its estimation. This is so because, at the beginning of the discharging, I In does not need to be constant; it is only strictly necessary that it be constant from T B to T A to obtain (9). Slight variations of I In at the start of the discharging process of C X due to C In and C m are therefore not important.…”

Section: B Error Analysismentioning

confidence: 99%

“…However, C A and C B affect the estimate of C X , limiting the accuracy and the lower limit of the capacitances that can be estimated by (9). This can be overcome with a simple offline autocalibration, requiring only two measurements (T A0 and T B0 ), removing the sensor in the circuit of Fig.…”

Section: B Error Analysismentioning

confidence: 99%

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Direct Interface Circuit for Capacitive Sensors Affected by Parasitic Series Resistances

Hidalgo-López

2023

IEEE Trans. Instrum. Meas.

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This article presents a novel circuit to directly interface a capacitive sensor affected by parasitic series resistances to a digital processor (DP). The presence of such resistances distorts the estimation of the capacitance to be measured. Current measurement procedures for these sensors, such as impedance-frequency characteristics, are complex and require significant hardware resources, power consumption, and time.To eliminate these drawbacks, a new circuit based on the so-called direct interface circuits (DICs) is introduced, which performs the digital reading of the sensors taking advantage of the presence of DPs in many applications. The hardware requirements in the new design are minimal: just two resistors and an operational amplifier in addition to the DP. The circuit requires only two time measurements to estimate sensor capacitance. These are obtained during a single capacitor charging-discharging process, simultaneously reducing power consumption and measurement time. The circuit has been implemented using a field-programmable gate array (FPGA), as the DP, in a general-purpose board to evaluate its performance. Although it is not an application-specific design, the circuit shows a maximum systematic error of 0.37% for capacitances in the 100 pF-96 nF range with parasitic series resistances up to 1200 . The maximum measurement time for this range is just 4.5 ms.

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Section: Introductionmentioning

confidence: 91%

“…There are a variety of sources of error in the estimate provided by (9). First, one must consider the parasitic capacitors that appear in the implementation of the circuit.…”

Section: B Error Analysismentioning

confidence: 99%

Section: B Error Analysismentioning

confidence: 99%

Section: B Error Analysismentioning

confidence: 99%

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Direct Interface Circuit for Capacitive Sensors Affected by Parasitic Series Resistances

Hidalgo-López

2023

IEEE Trans. Instrum. Meas.

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“…In the case of DCS, most proposals use different versions of a relaxation-oscillator and AC sources to find x C [23][24][25][26][27]. Errors are between 0.1% and 6.74% FSS.…”

Section: Introductionmentioning

confidence: 99%

A simple digital readout circuit for differential resistive or capacitive sensors

Hidalgo-López

2023

Meas. Sci. Technol.

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This paper introduces and analyses a novel direct interface circuit (DIC) that directly connects differential resistive and capacitive sensors to digital processors (DPs), performing a magnitude-to-time-to-digital conversion of the information they provide. The simple circuit performs the readout using two passive components, the differential sensor, and the DP. In some cases, the circuit may require an additional passive element. The DP only uses common digital resources such as bidirectional pins or a counter, meaning microcontrollers, FPGAs, or ASICs could all be used as DPs. Different DICs proposed in the literature for reading differential sensors require three time measurement processes to estimate the variable to be measured. The new circuit requires only one, saving time and energy dissipation, and reducing the number of error sources. A design based on an FPGA has been implemented as a proof of concept. Measurement times in the order of 1.1–1.3 ms have been obtained with this configuration. Errors in the readout of a differential resistive sensor are below 0.34% in the worst case and below 0.63% for a differential capacitive sensor.

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Performances evaluation and characterization of a novel design of capacitive sensors for in-flight oil-level monitoring aboard helicopters

Di Nisio,

Andria,

Adamo

et al. 2024

Measurement

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Simple and robust microcontroller-based acquisition system for differential capacitive sensors

Cited by 4 publications

References 26 publications

Direct Interface Circuit for Capacitive Sensors Affected by Parasitic Series Resistances

Direct Interface Circuit for Capacitive Sensors Affected by Parasitic Series Resistances

A simple digital readout circuit for differential resistive or capacitive sensors

Performances evaluation and characterization of a novel design of capacitive sensors for in-flight oil-level monitoring aboard helicopters

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