Strain transducer systems

This relationship has been exploited for NDT, where impedance transducers have been developed that measure the elastic strain at two different sections of a vibrating rod excited at one end and in contact with a composite structure at the other end. Certain impedance transducer systems measure the potential difference between a top driving piezoelectric element and a receiving piezoelectric element the relationship between these voltages is dependent on the impedance. It was reported by Cawley that a 3 dB difference in impe-... 

The cone and plate viscometer can be used for oscillatory shear measurements as well. In this case, the sample is deformed by an oscillatory driver which may be mechanical or electromagnetic. The amplitude of the sinusoidal deformation is measured by a strain transducer. The force deforming the sample is measured by the small deformation of a relatively rigid spring or tension bar to which is attached a stress transducer. On account of the energy dissipated by the viscoelastic polymer system, a phase difference develops between the stress and the strain. The complex viscosity behavior is determined from the amplitudes of stress and strain and the phase angle between them. The results are usually interpreted in terms of the material functions, p, G, G" and others [33-40]. 

The equipment required to measure in-phase and quadrature linear dichroic spectra consists of two components, the transducer necessary to provide the small amplitude oscillatory strain and a suitably modified infrared spectrometer. So far as the former is concerned, it is desirable that the transducer system is capable of operating over a range of frequencies, in order to provide the flexibility that may be required in probing a change of re-orientational responses. The transducer may either form part of a dynamic mechanical analyzer, as described by Noda et al. [17] or may be a simple unit used solely as part of an infrared spectrometer system. 

Fig.l shows the layout of the SPATE 9000 system. It basically consists of a scan unit connected to a signal amplifier. The signals are then correlated with a reference signal derived from a load transducer (e.g. strain gauge, load cell, accelerometer, or function generator). 

Of special interest in scale-control systems is the type in which the motion of the scale beam is sensed by a differential transformer or a group of load cells. The output of such devices is proportional to the displacement of the scale beam, which in turn is proportional to the amount of material in the weigh bucket. Many designs use loadsensing devices such as strain gauges or transducers. These eliminate the need for a scale-beam mechanism. The weigh vessel is mounted directly on the load-sensing devices. This provides many benefits in... 

Steady shear viscosities can be measured with two different instruments. The System IV can measure polymer viscosities from about 0.001 to 10 sec 1 while the Gottfert Capillary Rheometer is capable of obtaining viscosities from 0.1 to 100,0001/s. In steady shear, the strains are very large as opposed to the dynamic measurements that impose small strains. In the capillary rheometer, the polymer is forced through a capillary die at a continuously faster rate. The resulting stress and viscosity are measured by a transducer mounted adjacent to the die. A schematic of the system is illustrated in Figure 5. 

During clamping and when applying pressure on the molds, the tie rods stretch. If everything is in balance, the platens and mold stretch evenly. The distance the rods stretch is directly proportional to the applied load. Sensors, such as electrical strain gauges, can be used to detect the stretch or load applied and if an unbalance situation occurs, an indicator can alert the operator or the process control system. Bar sensing can also be used as a means of signaling the switch from pack to hold pressures, a potential alternate or support to pressure transducer use. 

Strain gauges and pressure transducers were attached at (k) 15.25 m (ft) intervals along the pipe and an accelerometer at (1) 29.3 m (ft) below the surface. The barge and pipe system, weighing a total of (m) 81,648 kg (ton) was anchored by (n) 22,680 kg (lb) concrete blocks on either side. A cable system held the barge in place. 

The most common method for reducing the effects of environmental inputs is isolation. Here, each of the measuring elements is effectively isolated from environmental changes. Examples are the placement of reference junction of a thermocouple in a temperature-controlled enclosure rmd the use of active vibration-isolation tables to isolate a measuring system (e.g., atomic force microscope) from external mechanical vibrations. Of course, it is possible to reduce environmental influences by selecting a transducer material that is completely insensitive to a specific environmental parameter. An example is the use of a metal alloy in strain gauges that has a zero coefficient of thermal expansion. But such an ideal material is often difficult to find and quite expensive. 

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