Mass transducers

TTie system can be used for continuous measurement of the mass concentration at a single point for up to 12 hours, for traverse measurements of stack particulate mass concentrations using sample probe extensions, with the mass transducer up to 6 m in the stack, or for intermittendy measuring particulate mass concentrations of emission gases for long-term readings (e.g.. 30-sec samples every 60 minutes. ... 

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). 

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. 

The high pressure thermobalance is very simliar to the balance described by Feldkirchner and Johnson (7). The thermobalance is designed to operate isothermally up to 1000 °C and 2000 psi hydrogen. Details of the balance are shown in Figure 1, and a schematic of the system is shown in Figure 2. The reactor tube is constructed of Haynes 25 superalloy. The mass transducer is a Statham model UC 3 attached to a balance arm (Micro-scale accessory UL 5) and has a full-scale range of 6 grams. 

More sophisticated mass transducers were proposed by using resonant cantilevers similar to those adopted in atomic force microscopy In spite of the claimed properties, these sensors were never demonstrated in practical applications. 

The QCM is a well-established piezoelectric mass transducer which can be used to measure mass changes lower than those of a nanogram order. It was reported that the (3-CD/T102 film imprinted with bisphenol A was prepared for the specific detection of bisphenol by QCM and cyclic surface-polarization impedance (cSPI) [67]. The thin y-CD/T102 film with a QCM transducer was used for selective detection of nitro aromatic compounds [68]. The detection was carried out via cyclic surface-polarization impedance spectroscopy. It was also established that (3-CD may be used for functionalization of the mesoporous silica film in order to improve the sensing of gases such as benzene and ethanol by QCM [69]. 

Muscle is the major biochemical transducer (machine) that converts potential (chemical) energy into kinetic (mechanical) energy. Muscle, the largest single tissue in the human body, makes up somewhat less than 25% of body mass at birth, more than 40% in the young adult, and somewhat less than 30% in the aged adult. We... 

The immobilization of the hyperbranched spherical structures onto physical transducers greatly increases the binding capacity of the surface and leads to enhanced sensitivity and extended linearity of biosensors. Nucleic acid dendrimers were prepared and their amplification properties for the detection of DNA were examined using mass-sensitive transducers [45, 46]. Antibodies... 

The micro reactor properties concern process control in the time domain and process refinement in the space domain [65]. As a result, uniform electrical fields are generated and efficiency is thought to be high. Furthermore, electrical potential and currents can be directly measured without needing transducer elements. The reactor fabrication methods for electrical connectors employ the same methods as used for microelectronics which have proven to satisfy mass-fabrication demands. 

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],... 

Rn-222 is produced from a dry Ra-226 source with an activity of about 2 mCi housed in a lead shield. Radon is carried from the source by means of compressed air with a regulated flow rate of 200 cnr/min. The test chamber is operated with a 75 1/min air pump located downstream (Figure 1XDroullard, et al., 1984) that exhausts to the outside of the building. The flow rate of this air pump is monitored by a mass flow transducer whose signals are converted to volumetric flow rates. 

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

Conductometric transducers, as the oldest electrochemical devices, seem not to enjoy wide applications due to their poor selectivity. For example, Yagiuda et al. proposed a conductometric immunosensor for the determination of methamphetamine (MA) in urine [89], The decrease in the conductivity between a pair of platinum electrodes might result from the direct attachment of MA onto the anti-MA antibodies immobilized on the electrode surface. The system was claimed to be a useful detection technique of MA in comparison with a gas chromatography-mass spectrometry method. 

Among various enzyme immobilization protocols, entrapment in polymer membranes is a general one for a variety of transducers. Formation of a membrane from a solution of already synthesized polymer is simpler and reproducible compared to chemical polymerization. The simplicity of this immobilization procedure should provide reproducibility for the resulting biosensors the latter is strongly required for mass production. 

---