It also monitors the energy dissipated by the sensor, which is used to determine the series resistance of the crystal. The controller provides power to the crystal oscillator electronics, and includes a potentiometer for canceling shunt capacitance. Proper capacitance cancellation is required to assure true series resonance operation of the crystal oscillator, and to eliminate frequency and resistance errors. In the QCM200, the digital controller also contains a frequency counter with 0.01 Hz resolution for accurate frequency measurements, and a resistance meter with 5 digits of resolution covering a range of 0 to 5000 Ω. The QCM200 uses a 5 MHz, 1" diameter, AT-cut quartz crystal wafer with circular electrodes on both sides. Crystals are available in a variety of materials. The crystal holder is a rugged, compact, easy to use fixture. The holder and all crystals may be used in liquid or gas environments.Īn optional axial flow cell adapter attaches to the standard crystal holder. This provides an easy way of interfacing the QCM to a flow injection analysis system.įor EQCM applications, an analog output proportional to frequency shift may be directly connected to a potentiostat or galvanostat. Only the front-surface electrode of the crystal is exposed to the solution. This electrode is also transformer isolated, as required for EQCM operation. The figure below illustrates a typical EQCM experiment. The frequency analog output of the QCM controller is connected to the potentiostat A/D input. The potentiostat digitizes the voltage, and it's software displays relative frequency changes synchronous with the electrochemical data. The versatile QCM200 can be easily integrated into any custom 5 MHz crystal based EQCM setup. The QCM200 is a valuable research tools for applications ranging from pure surface science to biochemistry. Quartz crystals can be pre-coated with any thin film material including organic polymers, hydrogels, composites, ceramics, biomolecules, bacteria and living cells. This provides unlimited potential for the development of novel gas and biological sensors. The quartz crystal microbalance is an essential addition to any biological laboratory. The data from a QCM perfectly complements that obtained from other techniques, such as surface plasmon resonance (SPR) and atomic force microscopy (AFM), aiding in the analysis of complex biological interactions.Shear tests on quartz rocks and single quartz crystals have been conducted to understand the possible relationship between the intensity of detectable stress in fault areas and the energy released in the form of electromagnetic waves in the range 30 KHz-1 MHz (LF–MF). For these tests, a new type of piston-cylinder has been developed, instrumented to collect the electromagnetic signals generated by the quartz during shear stress tests and that allows energy measurements on electromagnetic emissions (EMR) to be performed. The data obtained indicate that shear-stressed quartz crystals can generate electromagnetic emissions in the LF–MF range. These emissions represent a tiny fraction of the total energy dissipated in the fracturing process. The spectrum of radio emissions consists of continuous radiation and overlapping peaks. For the first time, a characteristic migration of peak frequencies was observed, proportional to the evolution of the fracturing process. In particular, the continuous recording of the radio emission spectra shows a migration of the peaks toward higher frequencies, as stress continues over time and smaller and larger fractures form.
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