/spl Sscr/tudy of the dynamic response of QCM sensors by means of a fast and accurate all-digital frequency detector

Low-Cost, Intelligent Data Acquisition System for QCM and Other Resonator-Based Bio- And Chemical Sensors

“…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]. All of these are built-up on a quartz piezoelectric substrate.…”

“…The change in resonant frequency (∆f) in Hz is directly proportional to the mass adsorbed on the crystal surface. As usually, a crystal has a characteristic resonance frequency (f 0 ) in the MHz range, whereas a deposition causes a shift (∆f) of the resonance frequency up to a few hundred of ppm [1]. There are several methods and systems for the sensor resonance frequency shift measurement, reported in literature.…”

A high-performance measurement system for simultaneous mass and resistance variation measurements on gas sensing polymer films

“…For this type of sensors, the frequency shift due to the gas sorption, and hence to the mass change, is the measured quantity. This parameter can be measured by means of simple equipment but significant sensor performance improvements can be obtained when exploiting the dynamical behavior of the resonance frequency [3]. This must be accomplished by using sophisticated measurement equipment such as the one presented in [3].…”

“…This parameter can be measured by means of simple equipment but significant sensor performance improvements can be obtained when exploiting the dynamical behavior of the resonance frequency [3]. This must be accomplished by using sophisticated measurement equipment such as the one presented in [3]. Moreover, a further improvement can be obtained with the simultaneous measurement of the polymer resistance as well as the QCM frequency [17,18].…”

All-digital interface ASIC for a QCM-based electronic nose

“…Some use the QCM as the resonant element in a digital logic-gate based oscillator circuit, the resulting oscillation frequency being measured by either a digital frequency counter implemented in a Field-Programmable Gate-Array (FPGA) [2,3], or a frequency-to-voltage converter driving an analog-to-digital PC data acquisition card [4,5]. Use of a more sophisticated oscillator design, formed from operational amplifiers and a voltage-controlled oscillator (VCO), permits the loading effect when the sensor is immersed in a liquid analyte to be compensated for, and thus may be used in a QCM-based electronic tongue [6].…”