Pressure measurement calibration

Figure 1.4.1 Pressure drop calibration and pump performance measurement. ...

The catalyst bed that was charged to the reactor is now a restriction, calibrated for flow vs. pressure drop. The pressure drop equals the pressure generated by the blower, which in turn depends on the RPM. In essence, the differential pressure measurement was eliminated by calibrating the flow directly with RPM. 

Good-quality Bourdon tube test gauges are highly suitable for pressure measurements of more than 20psi. They should be calibrated against a... 

The correct flow to use is the compressor suction. However, a flow element such as an orifice in the compressor suction can rob inordinate horsepower. Therefore, sometimes the discharge flow is measured and the suction flow computed within the controller by using pressure measurements. Other times the compressor intake nozzle is calibrated and used as a flow element. The correct AP to use is the discharge minus the suction pressure. 

One of the best and most convenient methods of measuring the flow in the terminal is to use the terminal characteristic pressure difference. This requires that the manufacturer of the terminal provide calibration curves, where the flow rate is expressed as the function of the characteristic pressure difference. Some devices have integrated pressure measurement tappings, and the user has only to attach a manometer to measure the pressure difference. 

The kinetics of the gas-phase reaction between nitrogen dioxide (A) and trichloroethene (B) have been investigated by Czamowski (1992) over the range 303-362.2 K. The reaction extent, with the reaction carried out in a constant-volume BR, was determined from measurements of infrared absorption intensities, which were converted into corresponding pressures by calibration. The products of the reaction are nitrosyl chloride, NOC1 (C), and glyoxyloxyl chloride, HC(0)C(0)C1. 

Since the density of Pt decreases by only 0.009 g cm- from 0 to 1200 bars, the effect of pressure on the density of Pt can be neglected if weights below 1 g are used. Both f and V were found to be functions of pressure (36). Calibrations of the float at a given pressure indicate that the precision of the system is 10 ppm while the accuracies are about 20 ppm (116). We have used this system to measure the relative densities of D2O (117), seawater 0.16,118), and some major sea salts (36, 119). 

In industry, the magnitude of surface tension can be monitored with the help of bubble pressure. Air bubbles are pumped through a capillary into the solution, and the pressure measured is calibrated to known surface tension solutions. Using a suitable computer, one can then estimate surface tension values very accurately. Commercial apparatus are also available to monitor surface tension. 

If vapour pressure measurements are to be an essential part of the work to be undertaken, a cold cathode manometer is probably the best choice, despite the fact that it needs to be calibrated for each molecular species, and its use with mixtures of gases containing two or more species is correspondingly more difficult. If such mixtures are to be investigated, or if the chemicals concerned are corrosive, it is probably most efficient to use a mechanical gauge as a null-point instrument and to measure the pressure by means of a McLeod gauge. 

In the experiments, pressure was measured with pressure gauge of the plunger type which transmitted pressure to calibrated manometers of high precision. During the first... 

The sequence of operations (assuming the initial solid is not air sensitive) would be to load the sample tube with a weighed amount of reactive compound and the stirrer, to attach this tube to the tensimeter, and to pump out the air in the tensimeter. The sample tube is cooled to liquid nitrogen temperature and solvent is then condensed into the sample tube from a storage container on the vacuum line. The main valve on the tensimeter is then closed and the sample container allowed to warm so the solid may dissolve, perhaps with the aid of the stirrer. A constant temperature slush bath is next placed around the sample tube as illustrated in Fig. 9.5 and an initial pressure measurement is taken on the manometer. Next, the first alloquot of the reactive gas is transferred from a storage bulb elsewhere on the vacuum system into the calibrated bulb using the techniques outlined in Section 5.3.G (the bubbler manometer shown in Fig. 9.5 is used for the pressure determination required for this process). This gas is con-... 

The beauty of the mercury manometer is that you can assess its accuracy by simply looking at it. If the mercury meniscus is at zero when there is no pressure in the cuff and the column moves smoothly with inflation and deflation it is accurate and can be used as the gold standard for pressure measurement. All other devices must be calibrated against a... 

The volumetric adsorption experiment [6] shown in Figure 6.2 consists of a thermostated sample cell of volume Vg at an experimental temperature, T, a container with a precisely determined volume, named the calibrated volume, Vc, a connection to the gas reservoir, and a transducer for pressure measurement. In addition, the volume at stopcock 3, at ambient temperature, Tv and the thermostat is denoted V2, and the volume between stopcocks 1, 2, and 3, also at ambient temperature, Tr, is denoted Vt. 

Because pressure transducers from different manufacturers can vary significantly, it is important to understand their performances such as accuracy. An ideal device would have a direct linear relationship between pressure and output voltage. In reality, there will always be some deviations this is referred to as nonlinearly. The best straight line is fitted to the nonlinear curve. The deviation is quoted in their specifications and expressed as a percent of full scale. The nonlinear calibration curve is determined in ascending direction from zero to full rating. This pressure will be slightly different from the pressure measured in descending mode. This difference is termed hysteresis it can be reduced via electrical circuits. 

Pressure Measurements The term mm Hg used with respect to pressure within an apparatus, or atmospheric pressure, refers to the use of a suitable manometer or barometer calibrated in terms of the pressure exerted by a column of mercury of the stated height. 

The quantity of molybdenum hexafluoride may be measured either in a preweighed vessel or by vapor-pressure measurements in a previously calibrated volume on the line. It was pointed out by the checker that while molybdenum hexafluoride is being handled in the line the stopcock D should normally be kept closed. 

The unit used to compare the computer line s pressure measurement readings with equipment air pressure measurements has not been calibrated. Additionally there has been no periodic maintenance to assure that the unit is operating appropriately. The issue becomes even more critical because the. .. computer system is not validated. It is essential that this unit. .. be accurate and reliable. [FDA Warning Letter, 1999]... 

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