Vacuum gauges manometer

Gauges. Because there is no way to measure and/or distinguish molecular vacuum environment except in terms of its use, readings related to gas-phase concentration ate provided by diaphragm, McCleod, thermocouple, Pitani gauges, and hot and cold cathode ionization gauges (manometers). 

S.6. Choice of gauges For the general operation of a vacuum system, a vacuum gauge is usually not required, but it may be useful, especially to the less experienced operator. For general monitoring purposes the small U-tube manometers and the Vacustat -type mini-McLeod gauge are adequate. 

Details on pumps, manometers, vacuum gauges, special apparatus, and leak testing are given in Chapters 6-10. It is the purpose of the remainder of this chapter to describe the transfer of condensable and noncondensable gases, trap-to-trap fractional separation of volatiles, and the use of vapor pressure in the characterization of volatile compounds. These operations are basic to practically all chemical vacuum line work. 

Figure 1. Schematic of apparatus A, calibrated variable-volume mercury burette B, reference volume C, main chamber D, mixing pump E, adsorption chamber F, reference chamber G, constant temperature baths H, mercury manometer J, cold-cathode gauge P, Pirani vacuum gauge R, mercury reservoir...

Stopcocks B, C, D, E, and of course G should be closed and the pressure determined with the vacuum gauge it should be 10 Torr or less. Now set the mercury level exaetly at the lower mark in the gas burette and close stopcock F. Also raise the mereuiy in the manometer to approximately the zero level. After closing stopcock A and opening C, D, and E, read the vacuum gauge again and also verily that the mercury level is the same in both arms of the manometer. 

The ozone, hydrogen, and oxygen pressures were measured by an H2SO4 manometer the O3 pressure was checked by optical absorption at 2537 A. The NH3 and He pressures were measured by an Alphatron Vacuum Gauge, Model 820. 

The steam feeding of the chamber is under the full control of the programmable logic controller (PLC) and data acquisition is achieved by the SCADA system during sterilization cycle control. Vacuum gauges are adapted to function in saturated steam and ambient conditions (MKS capacitance manometer 621). 

If instead of mercury, a silicone oil is used as manometer liquid, the precision of reading increases tenfold. Thus the Laporte manometer uses such a filling for the range of 0.2 to 20 torr. A vacuum gauge working on the displacement principle [35] which serves for precision measurements between 0 and 10 torr exhibits an accuracy of 0.01 torr. Vacuum pump oO, purified paraffin and AmoU S cannot be recommended as manometer liquids since they absorb water and thus yield appreciable errors [36]. Following a suggestion of Bachmann, in the case of water some additives should be used which reduce the surface tension. 

It would take us beyond the scope of this book to mention aU the vacuum gauges that are manufactured. They are fully described in the various monographs on high-vacuum technique [49]. In the 10 to 10 " range the Pirani gauge is much used and in the 10" to 10 range the ionization manometer. Combinations of these two instruments into a single unit are avaUable. 

Figure 9.16. A pressure controlled batch evaporating crystallizer A, 2 C crystallization vessel, B, baffle, C, stirrer, D, motor, E, variable speed controller, F, heating mantle, G, H, condensers, I, condensate receiver, J, drying tower, K, vacuum pump, L, contact manometer, M, electromagnetic valve, N, control box, P, electronic thermometer, R, vacuum gauge. After Mullin and Broul, 1978)...

The apparatus used to determine the pure component isotherms is illustrated in Fig. 1. This system consists simply of the adsorption cell, a constant temperature bath, a source of adsorbate (i.e., CH4), and a high-vacuum oil manometer to measure the adsorption pressure, TTie reference pressure of the manometer is monitored with a thermocouple vacuum gauge. Adsorption temperatures of 76 and 88.5 K were obtained with atmospheric baths of liquid N2 and respectively the other temperatures as measured with a copper-con-... 

Above 30 or 40 mm Hg of vacuum, an ordinary digital battery powered vacuum gauge is sufficient. However, only a vacuum mercury manometer is accurate in the 5 to 15 mm Hg range. As long as the mercury was dry, such a gauge gave excellent results. But few of my clients now permit the use of mercury in the field. 

In operation, the pressure was held constant at the desired value by using the signal from either an ion, thermocouple, or mercury manometer vacuum gauge to admit air through a controlled leak. Readings were then taken after thermal equi-... 

Capacitance manometer (vacuum technology) A vacuum gauge that uses the deflection of a diaphragm, as measured by the changing capacitance (distance) between surfaces, as an indicator of the pressure differential across the diaphragm, the pressure on one side being a known value. See also Vacuum gauge. 

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