Stepped-plate transducers

Gallego-Juarez JA, Rodriguez Corral G, Riera E et al. (2001) Development of industrial models of high power stepped-plate sonic and ultrasonic transducer for use in fluids. IEEE Ultrasonic Sypoos. Proceedings, pp 571-578... 

It should be noted that audible sound (generated by cheap loudspeakers) can be used for related separation techniques, even on large scales (pilot plant). A reduction in particle emissions from coal combustion fumes has been achieved using an array of stepped-plate piezoelectric transducers, which produce a homogeneous distribution of high-intensity waves (145-165 dB), located along the waU of the chamber at that high-temperature environment [135]. 

The basic setup to determine static interfacial tension based on either the Wilhelmy plate method or the du Noiiy ring method (see Alternate Protocol 2) is shown in Figure D3.6.1. It consists of a force (or pressure) transducer mounted in the top of the tensiometer. A small platinum (Wilhelmy) plate or (du Noiiy) ring can be hooked into the force transducer. The sample container, which in most cases is a simple glass beaker, is located on a pedestal beneath the plate/ring setup. The height of the pedestal can be manually or automatically increased or decreased so that the location of the interface of the fluid sample relative to the ring or plate can be adjusted. The tensiometer should preferably rest on vibration dampers so that external vibrations do not affect the sensitive force transducer. The force transducer and motor are connected to an input/output control box that can be used to transmit the recorded interfacial tension data to an external input device such as a monitor, printer, or computer. The steps outlined below describe measurement at a liquid/gas interface. For a liquid/liquid interface, see the modifications outlined in Alternate Protocol 1. Other variations of the standard Wilhelmy plate method exist (e.g., the inclined plate method), which can also be used to determine static interfacial tension values (see Table D3.6.1). 

Scanning the etalon and coarse tuner in tandem, the laser will tune in steps of the cavity FSR, c/21c, where Ic is the cavity length. Typical cavity FSRs are on the order of 300 MHz. Tuning the laser frequency between adjacent cavity modes can be achieved by smoothly increasing the cavity length by X/2. This is usually accomplished with a piezoelectric transducer (PZT)-driven cavity mirror or a tilted Brewster angle plate. To achieve smooth continuous scans, the three tuning elements must be synchronized. 

Stress relaxation for step squeezing of polystyrene at 180°C. (a) Stress versus time for increasing strain steps. Stress increases at short times, 2-10 ms because the plates take a finite time to close. The horizontal stress response signifies transducer overload. The rapid drop for strains e > 1 indicates loss of lubricant, (b) Stress relaxation data plotted as relaxation modulis. Solid line is the linear viscoelastic relaxation modulus calculated from shear dynamic data. Adapted from Soskey and Winter (1985). 

---