Miniature pressure transducers

To investigate the potential pressure gradients that exist within a laminate during autoclave processing, miniature pressure transducers (Fig. 10.5), which are capable of measuring the hydrostatic resin pressure, were embedded at multiple locations within several laminates to study the effects of vertical and horizontal pressure gradients [9]. 

W. H. Ko, J. Hynecek, S.F. Boettcher, Development of a miniature pressure transducer for biomedical applications, IEEE Trans. Electron Devices 1979, ED-26, 12, 1896-1905. 

The glucose-induced osmotic swelling pressure of the PBA-containing, glucose-sensitive hydrogel can be measured by confining it between a porous membrane and the diaphragm of a miniature pressure transducer. In this... 

Figure 8. Gas distributor housing miniature pressure transducer. Outside diameter is 18 mm.

Fung C D and Ko W H 1982 Miniature capacitive pressure transducers Sensors... 

PT 100 temperature sensor and miniaturized high-pressure transducer... 

The earthquake engineering experimental facility at Northeastern University provides large-scale dynamic testing of soil samples under uniform cyclic or earthquake motions. It includes a shaking table (Fig. 21.2), a data acquisition card (NI-DAQ) and software (LabVIEW), a set of instmments including accelerometers (Crossbow, Ig, 2g, 5g, Fig. 21.3a), linear variable displacement transducers (LVDT, RDP DCTH400AG, Fig. 21.3b), miniature pore pressure transducers (GE Druck PDCR 81, Fig. 21.3c), and multiple bender element and bending disk measurement equipment for S and P wave measurements (Fig. 21.3c-e). 

The stress component shown is simply the normal stress acting on the plate, and this method requires the measurement of the radial distribution of this stress. Miller and Christiansen [120] mounted very small pressure transducers in the plate to determine this distribution, but the development of a plate incorporating micro miniature sensors (MEMS) now makes this measurement much easier and more reliable [121,122]. 

An example of the pressure profile is shown in Figure 11.17, where the pressure was recorded in a miniature mixer [12]. Even though the size of the pressure transducer was large compared to the dimension of the rotor tip, a sharp rise in the pressure was registered when the rotor tip swept across the pressure transducer. The actual pressure peak may have been even steeper. 

Background. The term microsensor denotes a transducer that, in some fashion, exploits advanced miniaturization technology, whether an adaptation of integrated circuit technology, or some other microfabrication technique. Within the past decade, a myriad of microsensors have been developed, with capabilities for measurement of temperature, pressure, flow, position, force, acceleration, chemical reactions, and the concentrations of chemical species. The latter measurements, of chemical species, are intrinsically more difficult than the measurement of mechanical variables because in addition to requirements of accuracy, stability, and sensitivity, there is a requirement for specificity. 

Miniature transducer suited to the measurement of both hydrogen pressure and temperature. (Courtesy of Kulite.)... 

In (10) and (25)-(34) cam-follower experiments are described. In all test rigs the cam radius was of the order of 50 mm, while the cam width was of the order of 10 to 20 mm. Film thickness is estimated from global capacitance in (10), (25), (30) and (31), and from overall contact resistance in (26). Local film thickness measurements, employing the 0.25 mm dia. gauge described in (18), are reported in (29). The loads are rather low. This paper also shows pressure measurements obtained with a 0.25 mm effective dia. piezoelectric transducer. Local pressures and temperatures can also be obtained using miniature thin film transducers, see (27), (28), (32) and (33). These transducers have a minimum width of 10 pm. To find local cam surface temperatures, an infrared scanning system was employed in (34), with a spot size of 0.45 mm. 

Interference from water was eliminated by calibrating with a redox peak that was not proton related. Gas phase analysis showed strong redox signals for TNT and DNT and demonstrated that ILs serve as a preconcentrator to improve the sensitivity of very low vapor pressure analytes. These examples demonstrate that the combination of IL materials and electrochemical transducers overcomes many obstacles in forming an effective sensor system. IL-electrochemical sensors are also well suited for miniaturization and can be fabricated with very low cost. In contrast to nonspecific transducers such as a surface acoustic wave device, arrays of amperomertic and EIS transducers allow a secondary perturbation (e.g., potential) that enhances selee-tivity and increases analytical information content without increasing the number of physical sensor elements. 

---