Level measurements sonic methods

Accurate level measurement is also possible by use of ultra-sonic pulse transmission. The sound pulse is beamed onto the surface of the material/liquid to be measured and the time taken for it to bounce back to the source is converted into distance. This method is particularly useful in hazardous atmospheres. 

The theory of sonic-electronic level measurement is fundamentally based on a sound wave emission source from a transmitter, and a reflection of the sonic wave pulse to a receiver. Measurement of the transit time of this sound pulse and its correlation with electrical impulses provide a means for liquid level detection. Two basic designs operating on this principle use the vapor phase and the liquid phase methods. As most of the attention is currently devoted to the latter type system, this discussion deals exclusively with ultrasonic gaging over a liquid path. 

Infrared dichroism is one of numerous methods used to characterize molecular orientation. The degree of anisotropy of the strained pol3rmers may also be accurately characterized by other techniques such as X-ray diffraction, birefringence, sonic modulus, polarized fluorescence and polarized Raman spectroscopy [2]. These techniques directly probe the orientational behavior of macromolecular chains at a molecular level, in contrast to the macroscopic information provided by mechanical measurements. 

Although further analysis still must be completed before final regulatory thresholds can be proposed, it appears that for sonic of the toxicants, the health-based regulatory thresholds may be lower than the limit of detection of the available analytical method. This is especially so for some of the carcinogens. In such cases, EPA will probably set the regulatory threshold initially at the analytical measurement level planning to reduce it to the health-based regulatory threshold as methods are developed or improved. 

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