Pressure-sensitive elements

Strain-gauge pressure transducers are manufactured in many forms for measuring gauge, absolute, and differential pressures and vacuum. Full-scale ranges from 25.4 mm of water to 10,134 MPa are available. Strain gauges bonded direc tly to a diaphragm pressure-sensitive element usually have an extremely fast response time and are suitable for high-frequency dynamic-pressure measurements. 

A rupture disc is the pressure containing and pressure sensitive element of a rupture disc device. 

Fig. 6. Schematic design of a pressure sensor. A flexible stainless steel membrane interfaces the pressure-sensitive elements (bridged piezo-resistors) from the measuring liquid. Some products contain the amplifier electronics in the housing and are (somehow) temperature compensated. The shown 2-strand cabling mode resulting in a current signal is very convenient...

The first example of a large area pressure network fabricated on a plastic sheet by means of integration of organic transistors and rubbery pressure-sensitive elements was reported by Someya et al. [10] in 2003. The device structure is shown in Fig. 6.7. 

The calibrant included with the sample should have a number of desired qualities. It should have high symmetry and a small unit cell (to reduce the number of diffraction peaks that might overlap those from the sample) its volume should be strongly pressure dependent in order to maximise pressure sensitivity it should not react with the sample or the pressure transmitting fluid and it should be strongly scattering so that little of the calibrant is needed. Popular materials include NaCl [151],quartz [152] and a number of cubic elemental metals such as Pt,Au,Cu and Ta [153, 154]. The latter materials are most widely used for ultrahigh-pressure studies. 

Tack is, of course, of great importance for adhesives and many methods have been used. A summary of work on testing and finite element analysis of adhesive tack has been given136 and it has been questioned whether the methods used for pressure sensitive adhesives really work137. 

The inductance-type transducer consists of three parts a coil, a movable magnetic core, and a pressure sensing element. The element is attached to the core, and, as pressure varies, the element causes the core to move inside the coil. An AC voltage is applied to the coil, and, as the core moves, the inductance of the coil changes. The current through the coil will increase as the inductance decreases. For increased sensitivity, the coil can be separated into two coils by utilizing a center tap, as shown in Figure 7. As the core moves within the coils, the inductance of one coil will increase, while the other will decrease. 

Hyphens are employed to connect words that are compounded into adjectives-for example, a hot-wire anemometer, a high-pressure line -but no hyphen appears in a highly sensitive element. ... 

Many early analyses of time-dependent solid-propellant combustion employed the concept of a combustion time lag [4], [17], [57]-[60]. A given element of reactant material requires a certain amount of time to burn, and if a small pressure pulse is applied to a steadily burning propellant, then the regression rate will take a certain amount of time to reach its new steady level. As the simplest idealization of these observations, assume that a pressure change applied at time t has no effect on m until time t -f Tj, at which time m instantaneously assumes its steady-state value, at all x, appropriate to the new pressure. The interval T/ is the time lag, assumed here to be a known constant. If n is the pressure sensitivity [appearing, for example, in equation (7-41)], then in m(t) = m[l -f m (t)] and p(t) = p[l -f p (0] we have m (t) = np (t — t ), so that... 

Most of the previous algorithms for generating isothermal and or isobaric ensembles can be shown to be special cases of the Nose -Hoover approach. As noted by Frenkel and Smit [2], problems appear most often when one attempts to simulate fluctuations in the various ensembles, but the averages of quantities such as the average energy and the pressure tensor elements are less sensitive to the choice of simulation algorithm. 

Temperature relief valves for use on unvented hot-water systems are beyond the scope of this entry. Combined pressure and temperature relief valves became popular in the United Kingdom in the early 1990s, but these devices are merely pressure-relief valves with additional facility for actuation by a temperature-sensitive element. As the bore of a combined valve is not required to choke, the addition of a temperature-sensitive actuator... 

In addition to producing the sensing array using OFETs, this team also fabricated much of the peripheral drive circuitry using OFET-based logic elements and introduced a creative architecture in which the unit dimensions can be customized by cutting several elements with scissors and attaching them with a pressure sensitive adhesive [138]. 

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