Conductivity gauge

The principle of design of a heat conductivity gauge (TM) is shown in Fig. 2.30. Electrical energy is fed into the wire (2) in such a way, that the temperature of the wire is kept constant. This amount of heat per time is in the area 2 of Fig. 2.31 and is approx, propor-... 

If a heat conductivity gauge (TM) is offered, the additional price for a capacitance gauge, which is strongly recommended, should be requested. 

The sensing filament in the gauge head forms a branch of a Wheatstone bridge. In the TFIERMOTRON thermal conductivity gauges with variable resistance which were commonly used in the past, the sensing filament was heated with a constant current. As gas pressure increases, the temperature of the filament decreases because of the greater thermal... 

A thermal conductivity gauge uses a constant electric current to heat an element whose temperature is a linear function of gas pressure over a limited range. The temperature is typically measured with a thermocouple. In the popular Pirani gauge, a single metal filament is substituted for a thermocouple, and filament resistance is monitored [19]. The range of pressures detected by thermal conductivity gauges is — lO -lO 4 torr, which makes them useful for... 

Analysis of hydrogen mixtures with a thermal conductivity cell is well established. The most accurate measurements are obtained by use of a thermal conductivity gauge with the walls immersed in liquid nitrogen and the wire heated to 160° K. This is the teniperature when the difference in the rotational specific heats of orthpara-hydrogen is a maximum . Various modifications of thermal conductivity gauges have been made to improve their convenience in use . A room temperature flow analyser based on a thermal conductivity cell has been developed by Weitzel and White which is claimed to be as sensitive as low temperature units. Bridge current and temperature must be controlled very carefully, but the unit is relatively insensitive to changes in pressure and flow rate. 

Fig. 17. Schematic representation of the experimental equipment for transmission UV-VIS studies on zeolites. C Quartz cuvette IM ionization gauge CM capacitance manometer IP ion pump TM thermal conductivity gauge SP sorption pump MP mechanical pump 1 -4 gas inlet valves. From [30] reproduced by permission of The Royal Society of Chemistry...

Figure 13.1. Thin-film chip calorimeter based on the thermal conductivity gauge TCG 3880. Scheme (a) and micro-photograph of the frame and the membrane loaded with a sample (b). [Adapted, by permission, from Ray, V V Banthia, A K Schick, C, Polymer, 48, 2404-14, 2007.1...

The pressure measurements should always be done by capacitance manometers (CAs) and not by thermal conductive gauges. TM depend on the gas mixture (water vapor and permanent gases) and are not reproducible enough for BTM measurements details are given on pp 327, 328 in [2]. For leak testing no special equipment specifications are required. The leak rate for the chamber, e.g., <1 x 10 mbarL/s, and for the condenser, e.g., <1 X 10 mbarL/s, should be specified since it might be helpful to measure the chamber and condenser separately. The maximum tolerable leak rate in the two examples is <1 x 10 mbarL/s, if the DR data at 0.1%/h should have an error <10%. If a helium leak tester is not available in production, it should be specified for quotation. 

Fiber diameter and pore size can be tuned by varying parameters such as polymer concentration, ejection rate, solution viscosity and conductivity, gauge size, strength of the electrical field applied, and distance between the tip and collector. In addition, an electrically grounded rotating dmm can be used to induce preferential fiber orientation." ... 

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