Instrumentation, density measurements

A turbine flowmeter consists of a straight flow tube containing a turbine which is free to rotate on a shaft supported by one or more bearings and located on the centerline of the tube. Means are provided for magnetic detection of the rotational speed, which is proportional to the volumetric flow rate. Its use is generally restric ted to clean, noncorrosive fluids. Additional information on construction, operation, range, and accuracy can be obtained from Holzbock (Instruments for Measurement and Control, 2d ed., Reinhold, New York, 1962, pp. 155-162). For performance characteristics of these meters with liquids, see Shafer,y. Basic Eng., 84,471-485 (December 1962) or May, Chem. Eng., 78(5), 105-108 (1971) and for the effect of density and Reynolds number when used in gas flowmetering, see Lee and Evans, y. Basic Eng., 82, 1043-1057 (December 1965). 

By connecting manometer hoses to both output pressures given by the tube, the pressure difference Ap can be measured directly. The barometric pressure and the fluid temperature are required for the determination of the fluid density. The Pitot-static tube is not a suitable instrument for measuring low velocities. It can be applied in cases where the flow velocity is high... 

Cathodic protection and associated instruments have developed in-line with the changing monitoring demands of both the onshore and offshore industries. In particular, for potential and current density measurements, far greater quantities of data are sought and are required to be processed into an easily assimilated form. Thus cathodic protection instrumentation has benefited from an increased association with microprocessor-based data handling and storage systems. 

Peripheral bone mineral density measurements cannot be used for diagnosis because they do not correlate with central measurements. However, they are useful in identifying patients who are candidates for central DXA and who are at increased risk of fracture.5 It also may be useful in patients who have had multiple fractures or in low-risk patients. Additionally, peripheral measurement of bone mineral density generally is less expensive than central DXA and is easily accessible. Instruments used for peripheral bone densitometry are portable, which allows bone density to be measured in pharmacies and health-fair screening booths. 

The radiation emitted by radioactive materials is harmful to living matter. Small quantities of radioactive isotopes are used in the process industry for various purposes for example, in level and density-measuring instruments, and for the non-destructive testing of equipment. 

Beatty, S. et al. (2000a). Macular pigment optical density measurement A novel compact instrument. Ophthalmic and Physiological Optics 20 105-111. 

This chapter on micromeritics will deal specifically with surface area, porosimetry, and density measurements. It is designed to introduce the importance of the specific technique in pharmaceutics and briefly describe the theory, instrumentation, and data collection involved. Examples are presented to... 

The discussion in this section will focus on true, bulk, and tap densities. The procedure and instrumentation used for each type of density measurement will be outlined, and pharmaceutical applications involving density will be presented. 

The three most common ways of obtaining true density measurements are gas pycnometry (gas displacement), liquid displacement, and flotation in a liquid. These three techniques have been compared based on accuracy, ease of use, and instrumentation [63], and the results are summarized in Table 4. Gas pycnometry will be discussed in this section because of its wide use and ease of operation. 

TSR 15). The data (Tables IV-VI) suggest that this instrument provides a satisfactory method for measuring heat release, even in the horizontal mode. Furthermore, it can differentiate between those materials which are prone to release much heat rapidly and those which perform much better in terms of heat release. The reliability of smoke data is, in principle, lower than that of heat data. In order to establish some criteria, the Tables include SmkFct values at 5 min (in MW/m2), which will be compared with SmkFct and SmkPar values for the same materials tested in the Cone and with values of specific maximum smoke density measured in the NBS smoke chamber. 

The instrument constant B can be determined by measuring the t in two fluids of known density. Air and water are used by most workers (22). In our laboratory we used seawater of known conductivity and pure water to calibrate our vibrating flow systems (53). The system gives accurate densities in dilute solutions, however, care must be taken when using the system in concentrated solutions or in solutions with large viscosities. The development of commercial flow densimeters has caused a rapid increase in the output of density measurements of solutions. Desnoyers, Jolicoeur and coworkers (54-69) have used this system to measure the densities of numerous electrolyte solutions. We have used the system to study the densities of electrolyte mixtures and natural waters (53,70-81). We routinely take our system to sea on oceanographic cruises (79) and find the system to perform very well on a rocking ship. 

The sample size required depends on the viscosity of the sample, the cell size of the density measurement device and the refractive index instrument. The density measurement requires a sample size of about 7-10 ml and the measurement must be made after a stabihzation period with no flow. In contrast, the refractive index measurement is made on a flowing stream. 

Beryllium connections and contacts are employed for switchgear and relays. Beryllium oxide is used as substrata for electronic circuits. Cadmium is used in television and fluorescent light phosphors. Cadmium, nickel and mercury are employed in batteries such as "nicad" cells and mercury cells. Mercury is used in fluorescent lamps, electrical switches, and outdoor lamps, as well as instruments for measuring pressure, temperature, and density. Selenium is employed as a photoreceptor in copying machines, and as a semiconductor in rectifiers. Lead applications include lead add storage batteries, a component in color television glass, and, in its oxide form, use as a dielectric material. 

Particle Measurements. A variety of instruments is available for measuring the number density and size distribution of particles sampled from airborne platforms. This discussion is restricted to instruments that measure particles smaller than 50 xm (cloud droplets and aerosol particles) because these particles are of most interest to atmospheric chemists. 

Altitude-resolved measurements of ozone and other constituents are necessary for improving our knowledge of physical and chemical processes in the stratosphere. Limbviewing satellite instruments can measure density profiles of stratospheric constituents at a good altitude resolution (1-3 km). In addition, satellite-based measurements have a global geographical coverage. 

The use of a precision digital density meter as supplied by Mettler Instruments (Anton Paar, Ag.) appeared attractive. Few references on using density measurements to follow polymerization or other reactions appear in the literature. Poehlein and Dougherty (2) mentioned, without elaboration, the occasional use of y-ray density meters to measure conversion for control purposes in continuous emulsion polymerization. Braun and Disselhoff (3) utilized an instrument by Anton Paar, Ag. but only in a very limited fashion. More recently Rentsch and Schultz(4) also utilized an instrument by Anton Paar, Ag. for the continuous density measurement of the cationic polymerization of 1,3,6,9-tetraoxacycloundecane. Ray(5) has used a newer model Paar digital density meter to monitor emulsion polymerization in a continuous stirred tank reactor train. Trathnigg(6, 7) quite recently considered the solution polymerization of styrene in tetrahydrofuran and discusses the effect of mixing on the reliability of the conversion data calculated. Two other references by Russian authors(8,9) are known citing kinetic measurements by the density method but their procedures do not fulfill the above stated requirements. 

The use of precision density measurements for monitoring polymerization reactions can be done rapidly and automatically using commercially available instrumentation. The method is independent of the reactor size and design but suffers from sampling difficulties. The examples of this paper show the rapidity of data collection and three distinct sampling problems pump failure from either monomer attack or polymer scale formation, monomer phase separation in the density cell, and the lag time for rapid polymerizations. Techniques have or can be devised to avoid or reduce the influence of these problems. 

As previously discussed, the density of the fluid whose flow is to be measured can have a large effect on flow sensing instrumentation. The effect of density is most important when the flow sensing instrumentation is measuring gas flows, such as steam. Since the density of a gas is directly affected by temperature and pressure, any changes in either of these parameters will have a direct effect on the measured flow. Therefore, any changes in fluid temperature or pressure must be compensated for to achieve an accurate measurement of flow. 

Imhof, R.E., Berg, E.P., Chilcott, R.P., Ciortea, L.I., and Pascut, F.C. New instrument for measuring water vapour flux density from arbitrary surfaces. IFSCC Magazine, 5, 297, 2002. 

SERS spectra in Ag hydrosols were recorded using a Jobin-Yvon HG2S monochromator equipped with a cooled RCA-C31034A photomultiplier and a data acquisition facility. To reduce the thermal effects due to the laser light, a defocused beam with low power (20 mW) was used. Raman data were obtained with exciting lines supplied by Ar"- and Kr"- lasers (406.7, 413.1, 457.9, 488.0, 514.5, 520.8, 568.2, 647.1,676.4 nm) or by He-Ne laser (632.8 nm). AU spectra were corrected to account for monochromator and photomultiplier efficiency. Power density measurements were performed with a power meter instrument (model 362 Scientech, Boulder, CO, USA) giving 5% accuracy in the 300-1,000 run spectral range. 

The scientists at Leatherhead Eood Research (United Kingdom) developed an instrument to measure viscosity of oil. The principle of its operation is similar to that of a tuning fork. Dampening of the vibration of the tuning fork-like device depends on the viscosity, and resonance depends on the density of the surrounding fluid. Although the instmment was simple to operate, the actual determination of oil quality was difficult for the restaurant operators. 

There have been many attempts at quantitating paper and thin-layer chromatograms 41), but the simplest approach appears to be optical density measurements of the migrated spots. Many excellent scanning devices are now on the market. They are precise optical instruments capable of great accuracy where the optical measurements are concerned. The one used in this laboratory is the reflectance scanner of Beroza et al. 34) which uses double-beam fiber optics. 

---