Transducers mass sensors

The piezoelectric mass sensor presenis an excellent example of a transducer converting a property of the analyte, mass in this case, to a change in an electrical quantity, the resonant frequency of the quart/ crystal. This example also illusiralcs ihe dislinenon hciwecn a... 

In this chapter the basic principles of piezoelectric transducers will first be reviewed. Once we have covered the basics of the propagation of elastic waves through piezoelectric solids, we will turn to the study of how resonant structures respond to surface mass loading. The transformation of mass sensors into chemical sensors will be discussed in terms of existing work and the potential for future developments. 

According to the operating principle of the transducer, chemical sensors may be classified in optical, electrochemical, electrical, mass-sensitive, magnetic, and thermal sensors or sensors based on other physical properties such as radioactivity. The transducer part is responsible for the sensitivity of the device. 

Adjustable Workbench (PAW) instrument assembly. The SH shown in Figs. 3.15 and 3.16 contains the electromechanical transducer (mounted in the center), the main and reference Co/Rh sources, multilayered radiation shields, detectors and their preamplifiers and main (linear) amplifiers, and a contact plate and sensor. The contact plate and contact sensor are used in conjunction with the IDD to apply a small preload when it places the SH holding it firmly against the target. The electronics board contains power supplies/conditioners, the dedicated CPU, different kinds of memory, firmware, and associated circuitry for instrument control and data processing. The SH of the miniaturized Mossbauer spectrometer MIMOS II has the dimensions (5 x 5.5 x 9.5) cm and weighs only ca. 400 g. Both 14.4 keV y-rays and 6.4 keV Fe X-rays are detected simultaneously by four Si-PIN diodes. The mass of the electronics board is about 90 g [36],... 

Chemical sensors may be classified according to the operating principle of the transducer as optical, electrochemical, electrical, mass sensitive, etc. 

In broad terms, a flow-through sensor is an analytical device consisting of an active microzone where one or more chemical or biochemical reactions, in addition to a separation process, can take place. The microzone is connected to or incorporated into an optical, electric, thermal or mass transducer and must respond in a direct, reversible, continuous, expeditious and accurate manner to changes in the concentrations of chemical or biochemical species in the liquid or gaseous sample that is passed over it, whether forcefully (by aspiration or injection) or otherwise (gases). 

Sensors can be based on a variety of transduction mechanisms, including electrochemical, optical, mass, and thermal. Different types of sensors, along with their transduction mechanisms, will be discussed later in this report. All sensors possess a transduction element connected to supporting instrumentation. Selectivity is achieved via the transducer. The qualities of an ideal sensor obviously depend on the application, with different qualities necessary for sensors used in shipboard laboratories, towed sensors, or sensors deployed on long-term remote moorings. Depending upon the specific application, sensors should possess the following qualities. 

Successful development and implementation of various chemical sensors for ocean measurements (based on optical, electrochemical, or mass transducers) requires concomitant advances in the design or discovery of organic or inorganic molecules that interact selectively with the important ocean analytes. These developments are particularly important for in situ sensors where no separation of ocean components or addition of external reagents occurs before or during the measurement step. 

In addition, the analyzer can accept analog signals From other field-mounted analyzers or sensors such as flowmeters and pressure transducers. The signal can be sealed, digitized, and incorporated into special calculations to determine mass flow, therms per day, reactor yields, and so on. 

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