Compression vacuum gauges

According to the type of scale division, a distinction is made between two forms of compression vacuum gauges those with a linear scale (see Fig. 3.7) and those with a square-law scale (see Fig. 3.8). In the case of the compression vacuum gauges of the McLeod linear-scale type, the ratio of the enclosed residual volume Vc to the total volume V must be knovm for each height of the mercury level in the measurement capillary this ratio is shown on the scale provided with the instrument. In the case of compression vacuum gauges with a square-law scale, the total volume and the capillary diameter d must be known. 

Nowadays a shortened McLeod type compression vacuum gauge according to Kammerer is used to measure the partial final pressure of mechanically compressing pumps. Through the high degree of... 

Fig. 3.7 McLeod compression vacuum gauge with iinear scale (equatbn 3.1b)...

Principle of measurement with compression vacuum gauges... 

Fig. 3.8 McLeod compression vacuum gauge with square-law scale (equation 3.11)...

Compression vacuum gauges ensure a reading of the sum of all partial pressures of the permanent gases, provided that no vapors are present that condense during the compression procedure. 

The scale of compression vacuum gauges can be calculated from the geometric dimensions. This is why they were used in the past by official calibration stations as normal pressure (see equation 3.4.1a). 

Compression vacuum gauge (McLeod vacuum gauge)... 

The sample is 100 cubic feet (STP) of air compressed into a bottle containing 100 cc STP of active krypton and 75 cc STP of active xenon. Average yields are about 90% for krypton and 95% for xenon. The time required for the separation is about 8 hours of which 3 hours are spent in bleeding the sample into the system. Before the run all charcoal traps have been heated to 350 C and pumped on until the thermocouple vacuum gauge in the manifold... 

Fig. 2.13. The Vacustat or swivel gauge. This instrument is plugged into an outlet from the vacuum line by means of the horizontal B.14 cone A (see (c)). The normal position of the gauge is, as shown in (a), horizontal, so that the whole of it is evacuated the mercury is in reservoir B. When a measurement of the pressure is to be made, the instrument is turned into the vertical position, (b), so that the mercury traps the content of bulb D and compresses it into capillary which has the same diameter as capillary E. The pressure of the gas compressed into is given by the difference in height of the mercury in E and E. ...

We will need to use this table to calculate a jet s compression ratio, when we measure vacuum pressures with an American-type (in Hg) gauge. 

A tilting McLeod gauge is used to measure very low pressures of gases in glass vacuum lines in the laboratory. It operates by compressing a large volume of gas at low pressure to a much smaller volume so that the pressure is more easily measured. What is the pressure of a gas in a vacuum hue if a 53.3-mL volume of the gas, when compressed to 0.133 mL, supports a 16.9-mm column of mercury ... 

Fig. 5.5. Schematic view of industrial extrusion apparatus. (1) Endless screw (2) paste inlet (3) compression (4) vacuum (5) pressure gauge (6) vacuum cheunber (7) die.

Vickers hardness (HV) from RT to 800°C (hot hardness) was measured in a vacuum of 10"3 Pa at a 9.8 N load for 1 min. There is a valid reason to use the 1 min hardness for estimation of yield strength as Ctbend = HV/3 [5-7], As shown our compression tests at a strain rate of 6 -10"4 s"1 (Table 1), this estimation for the alloys under studying is quite efficient, and is valid within just a few percent.Bending tests were performed using three points technique on as-cast samples of 25 mm gauge length and 1x4 mm2 gauge section at ambient temperature. 

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