A very accurate measurement system for multielectrode capacitive sensors

Fac. of Electr. Eng., Delft Univ. of Technol.
IEEE Transactions on Instrumentation and Measurement (Impact Factor: 1.79). 05/1996; 45(2):531 - 535. DOI: 10.1109/19.492781
Source: IEEE Xplore


A very accurate capacitance-measurement system consisting of a
discrete capacitance-dependent oscillator and a microcontroller has been
developed. It can measure multielectrode capacitors with capacitances up
to 2 pF, with an accuracy of 100 ppm with respect to a reference
capacitor. The resolution amounts to 50 aF with a total measurement time
of 300 ms

29 Reads
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    • "The coating PUF capacitances are measured on-chip by means of a switched capacitor relaxation oscillator. High measurement accuracies (effects due to environment, voltage, temperature, and circuit inaccuracies can be eliminated) are reported [12]–[14] for this type of measurement method. A stable current source charges the selected capacitor until a certain threshold voltage is reached. "
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    ABSTRACT: Planar inter-digitated comb capacitor structures are an excellent tool for on-chip capacitance measurement and evaluation of properties of coating layers with varying composition. These comb structures are easily fabricated in a single step in the last metallization layer of a standard IC process. Capacitive coupling of these structures with a coating layer is modelled based on the electric field distribution to have a detailed understanding of contributing capacitance components. The coating composition is optimized to provide maximum spread in capacitance values of comb capacitor structures. This spread in measured capacitance values can be used to implement a physical uncloneable function (PUF). A PUF is a random function which can be evaluated only with the help of a physical system. We present an on-chip capacitive PUF for chip security and data storage in which the unlock key algorithm is generated from capacitors which are physically linked to the chip in an inseparable way. The strength of this key increases with the spread in capacitance values and measurement accuracy.
    IEEE Transactions on Semiconductor Manufacturing 03/2009; 22(1-22):96 - 102. DOI:10.1109/TSM.2008.2010738 · 1.00 Impact Factor
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    • "This capacitance will affect the noise performance of the interface (see section 3). As presented in [11] [12], the period of the relaxation oscillator equals "
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    ABSTRACT: This paper presents a high-performance interface for grounded conductivity sensors. The interface mainly consists of a sensor driver, an analog front-end, a multiplexer and a voltage-to-time converter. The sensor driver and analog front-end provide a controlled excitation voltage for the sensor and convert the sensor signal (conductance) into a voltage signal. The voltage-to-time converter acts as an asynchronous converter that employs a relaxation oscillator to convert the sensor signals (voltages) into a period-modulated output voltage. The analysis and experiments are performed to optimize the interface circuit with respect to the range of measurable conductance. With a prototype, over a wide conductance range, from 0.01 µS to 1 mS, the experimental results show random errors with a standard deviation of less than 5.6 nS for a measurement time of 160 ms, and a systematic error of less than 22 nS.
    Measurement Science and Technology 11/2008; 19(11). DOI:10.1088/0957-0233/19/11/115202 · 1.43 Impact Factor
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    • "The jitter due to the current noise of the amplifier decreases with an increasing value of . However, when the oscillator frequency is too high, approaching to , the nonlinearity of the conversion from the capacitance to the period of the oscillator will increase [3], [5]. By choosing , we assure that the nonlinearity due to this high-frequency influence is less than 10 . "
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    ABSTRACT: This paper presents the analysis and experimental results on the noise performances of a capacitive-sensor interface. The interface is able to measure low capacitance values in the order of picofarads and is implemented with a simple relaxation oscillator, a fast counter, and a microcontroller. The goal is to find the criteria to implement a low-noise system, so that, even with a short measuring time, low noise can be obtained. Experimental results are performed in order to prove the validity of the theoretical analysis. The achieved resolution, with a measuring time of 20 ms, was better than 14.2 × 10<sup>-7</sup> for the measurement of a capacitance value of 2.2 pF.
    IEEE Transactions on Instrumentation and Measurement 11/2005; 54(5-54):1934 - 1940. DOI:10.1109/TIM.2005.853684 · 1.79 Impact Factor
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