Manometers, electronic measuring

The manometers described here have a range of about 1-150 mm Hg in pressure. They are convenient to use when an aspirator is the source of vacuum. For high-vacuum systems (pressures below 1 mm Hg), a more elaborate manometer or an electronic measuring device must be used. These devices will not be discussed here. 

G. Bourdon Gauges. As an alternative to mercury manometers there is a variety of gauges based on mechanical or electrical pressure transducers. This section presents a description of purely mechanical gauges which still find use in this electronic age.4 The metal Bourdon gauge (Fig. 7.5) is fashioned around a semicircular thin-walled metal tube with mechanical linkage to a pointer. Fused-quartz spiral gauges are also available. In this case, a thin spiral is sensitive to a pressure differential, and the deflection is balanced with air pressure in the surrounding envelope. The air pressure is then measured with a manometer. 

Electronic manometers provide a convenient method of pressure measurement in a tensimeter, and the general arrangement may be very simple (Fig. 9.3). The one problem which must be anticipated is long-term zero pressure drift, which can be encountered with an electronic pressure gauge. Drift is minimized by maintaining a constant temperature on the pressure transducer and by avoiding mechanical vibration at the transducer. 

We chose to use a modernized version of the manometric measuring technique both in our earlier work and in the present experiments. This approach offered good flexibility in that the electronic manometers used to monitor the gas flux respond to a wide variety of gases. It is also possible to calibrate the apparatus reliably using existing standards. By completely computerizing the measurement process (6) we were able to provide... 

Extensive quantitative data were obtained by airflow modeling. A miniature calibrated Pitot tube, combined with an electronic manometer was used to measure the... 

From the point of view of field insfrumentation for measuring pressure inside fhe combustion chamber, it is possible to use either a glass U-tube manometer filled with fluorescent liquid or an industrial manometer for local measurements and an electronic pressure sensor for remote measurements and collection of data. Reliability and ability to dampen the pressure fluctuation inside the combustion chamber are the advantages of the U-tube and robust industrial manometers. 

The model is three-dimensional. In order to comprehensively analyze the distribution of flow field, 260 sampling points for 4 levels in goaf are sampled in a short time, and then the gas concentration of samples was analyzed and tested by GC-4000 A gas chromatograph. The sampling points are also used as pressure measurement points. The static pressure of points are absorbed by the YJB-1500-type compensator micro-manometer, and the wind speed and static pressure of intake and return airway were measured by electronic wind instrument and U-type differential pressure meter. 

Modem equipment uses electronic pressure sensors instead of Hg-manometers and digital technique to measure the vapor pressure. Also thermostating is more precise in recent apparatuses. The apparatus developed by Haynes et al. is shown in Figure 4.4.5 as example. 

The direet pressure measurement has the advantage that absolute pressures can be obtained and pressure fluetuations can be observed. More modem equipment applies electronic pressure sensors instead of Hg-manometers to avoid the problems caused by the... 

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