Pressure Measurements, Methods

Osmotic pressure is one of the colligative properties of solutions containing both low-Molecular weight compounds and high polymers. The major difficulty faced in the study of the behaviour of low Molecular weight compounds in solution by the Osmotic pressure measurement method is the selection of a suitable semi-permeable membrane. 

Examples of fundamental pressure measurement methods (as standard methods for ealibrating vacuum gauges)... 

Secondary Pressure Measurement methods their range and accuracy [11],... 

Pressure is measured extensively in the chemical processing industries and a wide variety of pressure measuring methods has been developed. Some of these have already been discussed in Volume 1, Section 6.2.2, viz. the manometer (which is an example of a gravity-balance type of meter), the Bourdon gauge (an example of an elastic transducer) and mention is made of the common first element in most pressure signal transmission systems—the differential pressure (DP) cell (Volume 1, Section 6.2.3). The latter also frequently forms part of a pneumatic transmission system and further discussion of this can be found in Section 6.3.4. 

Experimentation and novel measurement techniques are cmcial for the further development of microfluidic devices. Pressure is one basic parameter involved in microflmdic experiments. However, it is not realistic to apply the conventional pressure measurement techniques to microsystems, since the characteristic dimension of these measurement instruments is already comparable with the size of the microdevices. Therefore, novel pressure measurement methods are needed for pressure measurement at the microscale. 

Pressure Measurements, Methods, Fig. 1 Installation of the pressure sensor to a microchip (Reprinted from [5] with permission from Dr. Kitamori)... 

Pressure Measurements, Methods, Fig. 2 (a) Schematics of liquid pressure measurement, (b) Schematics of air pressure measurement, (c) Snapshot of liquid pressure measurement in microchannel P = 7,000 Pa), (d)... 

Pressure Measurements, Methods, Fig. 5 The schematic of the microchaimel and external pressure transducer. Details (i) glass slide, (ii) PDMS layer, (hi) transducer port, (iv) Unking tube, (v) transducer tubing, (vi) main channel port, (vii) pressure transducer (Reprinted from [15] with permission from Dr. Shen and American Institute of Physics)... 

Channel sizes in microfiuidic application are in the range of 10-1,000 pm. Therefore, pressure measurement methods or devices should be compatible with microchannels with different channel size. Flexible pressure measurement methods which can cover this size range are still a challenge. 

Pressure Measurements, Methods, Table 1 Summary of the characteristics of the measurement techniques... 

The differential pressure measurement method makes it possible to eliminate pump pressure noise and provides an analytical result which is indepen-... 

H. B. Jones, Transient Pressure Measuring Methods, Princeton University, Aero. Eng. Report No. 595a, 1963. 

An in situ pressure measurement method based on Raman microspectrometry has been developed. Pressure profiles and maps have been measured within a rolling EHL point contact for a wide range of operating conditions. The experimental pressure profiles were compared quantitatively with the numerical solutions of the isothermal EHL problem. These comparisons allowed a validation of the experimental method developed and showed the occurrence of thermal effects in the inlet of the contact at high speeds. Furthermore, it is possible to estimate the inlet temperature rise of the lubricant and the film thickness in the contact. 

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