A Direct Digital Readout Circuit for Impedance Sensors

Vooka, Prashanth; George, Boby

doi:10.1109/tim.2014.2361552

Cited by 47 publications

(14 citation statements)

References 23 publications

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“…Next section discusses the possible methods to correct or reduce this error, so that the CDC can complete the conversion in a few cycles of the input excitation. This, significantly, improves the conversion rate compared to the scheme presented in [24].…”

Section: A Non-linear Systematic Error and Conversion Ratementioning

confidence: 91%

“…The frequency f = 1/T, where T is the period of the sine wave. The CDC has an auto-zero phase followed by a conversion phase [24]. And, the conversion has a preset integration period (= T 1 ) and a de-integration period T 2 as illustrated in Fig.…”

Section: Dual-slope Capacitance-to-digital Convertermentioning

confidence: 99%

“…Thus, the associated error will be relatively small if a large value can be chosen for N 2 . But, this directly increases the conversion time [24], leading to very low conversion rates. Next section discusses the possible methods to correct or reduce this error, so that the CDC can complete the conversion in a few cycles of the input excitation.…”

Section: A Non-linear Systematic Error and Conversion Ratementioning

confidence: 99%

“…As explained earlier, by employing the special clock, and using the counts N SP1 and N SP2 , the error described in section-II-C, when the CDC uses a normal clock, is substantially reduced. With this new method, the number of excitation cycles required for conversion can be reduced drastically and hence a much higher conversion speed than in [24] can be obtained.…”

Section: An Improved Cdcmentioning

confidence: 99%

“…An impedance-to-digital converter (IDC) [24] reported recently, uses a sinusoidal excitation for the sensor and performs the impedance-to-digital conversion based on the dual-slope technique. It can provide a digital output of the sensor capacitance (C x ), independent of the value of R p .…”

Section: Introductionmentioning

confidence: 99%

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An Improved Capacitance-to-Digital Converter for Leaky Capacitive Sensors

Vooka

George

2015

IEEE Sensors J.

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This paper presents a capacitance-to-digital converter (CDC) that employs a novel approach to perform accurate measurement of capacitance of a leaky capacitive sensor. This CDC employs a sinusoidal source for excitation, which is advantageous for various sensing applications including ice detection, liquid level measurement, humidity measurement, proximity sensing, etc. Recently, an Impedance-to-digital converter (IDC) based on the dual-slope conversion technique has been reported. It can measure the value of capacitance even when a parallel resistance is present, but requires a large number of sinusoidal excitation cycles to complete a conversion, leading to poor update rate. The CDC proposed in this paper gives much higher (about 125 times) update rate compared to the IDC as it requires only a few excitation cycles for the conversion, but still gives an accurate output due to the use of a specially designed clock which helps to count the number of charge packets received by the integrator capacitor during the de-integration. Other than the operation of the CDC, the paper also describes outcome of a thorough analysis conducted to quantify the effect of various circuit parameters on the output of the new CDC. A prototype of the improved CDC has been developed and its performance parameters such as accuracy (± 0.27%), conversion time (24 ms), effect of parallel resistance, etc. have been tested and the results are reported in the paper.

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Section: A Non-linear Systematic Error and Conversion Ratementioning

confidence: 91%

Section: Dual-slope Capacitance-to-digital Convertermentioning

confidence: 99%

Section: A Non-linear Systematic Error and Conversion Ratementioning

confidence: 99%

Section: An Improved Cdcmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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