Pressure measurement instruments

Mechanical manometers are the oldest, simplest, and most reliable pressure measurement instruments. They have some disadvantages, which is one reason the use of electrical manometers is expanding. Their simplicity and fundamental nature can, however, be an advantage. 

As well as measurement errors due to the pressure measurement instrument itself, other errors related to pressure measurements must be considered. In ventilation applications a frequently measured quantity is the duct static pressure. This is determined by drilling in the duct a hole or holes in which a metal tube is secured. The rubber tube of the manometer is attached to the metal tube, and the pressure difference between the hole and the environment or some other pressure is measured. 

Measurement of relative humidity depends on the system used. Systems employing vacuum are usually evacuated prior to introduction of water vapor [29]. For cases in which there is not a gas-forming reaction occurring, measurement of total pressure in the system can be used as a measure of water vapor pressure. Systems in which air is not evacuated require specific measurement of water vapor pressure. (For the latter type of system, caution should be taken to assure that the relative humidity source is in close proximity to the solid, since the diffusion of water vapor through air to the solid is required to maintain a constant relative humidity in the immediate vicinity of the solid.) A wide variety of pressure measuring instrumentation is commercially available with varying accuracy, precision, and cost. 

Pressure. Pressure, defined as force per unit area, can be expressed as an absolute or relative value. Although atmospheric pressure constantly fluctuates, a standard value of 101.3 kPa (14.7 psia) has been assigned as the accepted value at sea level. The MaM in the psia stands for absolute, ie, the pressure is 14.7 psi (101.3 kPa) above zero pressure or a vacuum. Most ordinary pressure-measuring instruments do not measure true pressure, but rather a pressure relative to the barometric or atmospheric pressure. This relative pressure is called gauge pressure. The atmospheric pressure is defined to be 1 psig, in which the "g" indicates that it is relative to atmospheric pressure. Vacuum is the pressure below atmospheric pressure and is, therefore, a relative pressure measurement as well. The relationship between absolute and relative pressure is shown in Figure 3 (see Pressure measurement, Vacuum technology). 

STATE the three functions of pressure measuring instrumentation. 

After eliminating the effects of the pressure measurement instrumentation, electrokinetic and roughness effects were studied. 

The study of mine pressure regularity is mainly achieved through the analysis of hydraulic support column pressure. Hydraulic support column pressure measurement instrument adopts CDW-60 type hydraulic support pressure recorder. Support pressure measurement uses the station layout namely,... 

The Mercury Manometer.—For pressures not exceeding 130 kPa the pressure-measuring instrument will usually be a mercury manometer, by means of which the pressure is related to the fundamental quantities of length ii.e. the height of the mercury colmnn) and the density of the mercury. In amplification of what follows, one introductory and two comprehensive articles on the principles of barometry will repay study. 

The fluid static pressures were measured with calibrated Bourdon tube gages, and the differential pressures were measured with mercury-filled, double-legged glass manometers. These pressure measuring instruments were located on a single panel and their indications were recorded photographically. The fluid and wall temperatures were measured with copper-constantan thermocouples and recorded on multipoint temperature recorders. 

The sodium pools are mainly composed of a main vessel and guard vessel, with a temperature and pressure measurement instrument on the wall and a sodium leak detector in the gap of the vessels. The main vessel acting as the boundary of the primary circuit is a very important item of safety equipment. The internal strucmres involve the inner pool used to separate the hot and cold pools, the reactor core and its pressure header, and supports and shieldings. 

A3.4.2 Electric pressure measuring instruments must be checked at least once per month. Tensimeters must be observed routinely to ensure that the boiling inside is crisp and clean. Any tendency to foam indicates possible contamination. In that case, clean and recharge the instrument to restore accuracy. 

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