Abstract
A low-cost, intelligent data acquisition system for quartz crystal microbalance (QCM) and other (superficial SAW and bulk acoustic wave) resonator-based chemical and biosensors described in this article. The system is based on the novel modified method of the dependent count and allows obtaining high metrological performances: programmable and constant in all frequency range relative error of measurement up to 0,0005 % (5 ppm); nonredundant, reduced conversion time of measurement and wide frequency range from 0.05 Hz to 9 MHz (144 MHz with prescaling). The developed system allows measuring variations of the resonance frequency shift for QCM sensors working in liquids and gases. The described low-cost data acquisition system is based on novel integrated circuit of universal frequency-to-digital converter. This design approach has eliminated much of the hardware: there is no need for a microcontroller and complex sensor interfacing electronics, as it is directly compatible with PC computers.
Highlights
Many modern “electronic noses”, “tongues” and various precision applications for analytical chemistry are based on different chemical, mass variation sensors: quartz crystal microbalance (QCM), superficial SAW and bulk (BAW) acoustic wave sensors [1,2,3,4]
Due to its non-redundant and reduced time of measurement the developed system can be used for a chemical transient time constant and different dynamic behaviours determination in order to exploit a kinetic for adsorption processes. Such kind of low-cost frequency measuring systems are based on the UFDC-2 can be used in full system-on-chip electronic noses and tongues. This approach has eliminated much of the hardware associated with most measuring systems for QCM sensors; there is no need for a microcontroller in the system and complex sensor interfacing electronics as it is directly compatible with an IBM PC compatible computers and use only one IC
The data acquisition system for QCM and other resonator-based chemical and biosensors described in this article is based on the novel frequency measurement technique using the modified method of the dependent count and allows obtaining high metrological performances: programmable, constant in all frequency range, relative error of measurement up to 0.0005 % that corresponds to 5 ppm; nonredundant, reduced conversion time of measurement and wide frequency range from 0.05 Hz to 9 MHz (144 MHz with prescaling)
Summary
Many modern “electronic noses”, “tongues” and various precision applications for analytical chemistry are based on different chemical, mass variation sensors: quartz crystal microbalance (QCM), superficial SAW and bulk (BAW) acoustic wave sensors [1,2,3,4]. 2) Most likelihood methods based on a signal approximation by the sine curve set or by the use of rejection filters These methods have a high accuracy of frequency estimation but they need complex calculations. Using a method of reducing the risk of miscloking in the digital mixer the expected error of such system can be 0.06 ppm This measure leads to significant input frequency range narrowing (up to 7.006 ÷ 7.030 MHz) because of it needs a proper selection of the minimum difference of input frequencies that can reduce the probability of misclocking events to insignificance. As usually frequency counter-based systems has absolute error ± 1 Hz at 1 s measuring time Such solution is expensive, needs complex automatization for experiment and is not suitable for industrial systems of analytic chemistry
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