INFICON CATALOG 2000-2001 - Schoonover, Inc.

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Vacuum Gauges Contents General Basic Terms of Vacuum Metrology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.3 Transmitter Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.4 Measurements Units Conversion Chart . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C1.3 Sensors SKYª Capacitance Diaphragm Gauge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.6 CDG025, CDG045 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.6 CDG045-SD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.9 Bayard-Alpert Pirani Gauge BPG400 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.12 Pirani Standard Gauge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.15 PSG400, PSG400-S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.15 PSG100-S, PSG101-S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.17 Bayard-Alpert Gauge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.19 BAG100-S, BAG101-S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.17 Penning Gauge PEG100 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.22 Controller Vacuum Gauge Controller VGC103 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.24 Cables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.25 Vacuum Switch Vacuum Switch VSA100. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.27 Calibration Calibration Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B6.28 B6.2
Basic Terms of Vacuum Metrology Vacuum Gauges Basic Terms of Vacuum Metrology Today, the total range of measurable vacuum pressure extends from atmospheric pressure (about 1000 mbar, 750 Torr) down to 10 -12 mbar (Torr) Ð over 15 decades. The instruments used for measuring pressure within this wide range are called vacuum gauges. It is impossible to create a single vacuum sensor capable of performing quantitative measurements throughout the entire pressure range. Therefore, a variety of different vacuum gauges are available, each with its own characteristic measurement range, commonly extending over several decades. Note the difference between direct and indirect pressure measurements. With direct pressure measurements, vacuum gauge readings are independent of gas type. Vacuum gauges, in which pressure is determined directly by recording the force acting on the surface of a diaphragm, are common. With indirect pressure measurements, pressure is determined as a function of a pressure-dependent property of the gas (i.e. thermal conductivity or resulting ion current). These properties not only depend on pressure, but also on the molar mass of the gases. Therefore, vacuum gauge presssure readings relying on indirect pressure measurements are gas composition dependent. These readings usually relate to air or nitrogen as the measurement gas. Appropriate correction factors must be applied for the measurement of other gases or vapors. Vacuum Gauges with Pressure Readings Independent of the Type of Gas Capacitance Diaphragm Vacuum Gauges A capacitance diaphragm gauge has two chambers. One is connected to the vacuum to be measured; the other holds a certain reference vacuum. The chambers are separated through a metal coated ceramic or thin metal membrane. Together with a parallel electrode this membrane functions as a condensator. When the pressure in one chamber is different from the pressure in the other chamber the membrane bends and thus changes the capacitance. The change is registered and converted into a pressure signal, a voltage proportional to the pressure. This method makes gas type independent absolute pressure measurement possible. Absolute capacitance gauges can accurately measure pressures from 10 -5 mbar (Torr) to well above atmospheric pressure using capacitance gauges having diaphragms of different thickness. 1) <strong>INFICON</strong> improvements in materials composition provide more stable and reliable measurements over an extended period of operation. At the same time, corrosion resistance is greatly enhanced by using ceramic instead of metal. Vacuum Gauges with Pressure Readings Depending on the Type of Gas Thermal Conductivity Vacuum Gauges (Pirani) The energy transfer from a hot wire by a gas can be used to measure the pressure. The heat is transferred into the gas by molecular collisions with the wire, i.e. by heat conduction and the rate at which the heat is transferred depends on the thermal conductivity of the gas. The heat loss from a wire (typically 5 µm to 20 µm in diameter) can be determined indirectly with a Wheatstone bridge circuit which both heats the wire and measures its resistance and therefore its temperature. A thin metal wire is suspended with at least one side electrically insulated in the gauge head and is exposed to the gas. Tungsten, nickel, iridium or platinum may be used for the wire. The wire is electrically heated and the heat transfer is electronically measured. There are three common operating methods: constant temperature method, constant voltage bridge, and the constant current bridge. All these methods indirectly measure the temperature of the wire by its resistance. This measurement principle uses the thermal conductivity of gases for pressure measurements from 10 -4 mbar (Torr) to atmospheric pressure. <strong>INFICON</strong> improvements in temperature compensation provide stable pressure readings in spite of large temperature changes, especially when measuring low pressures. Ionization Gauges When the pressure in a vacuum system is below about 10 -4 mbar (Torr), direct methods of measurement of the pressure by means such as the deflection of a diaphragm or measurement of bulk gas properties such as thermal conductivity are no longer readily applicable. Hence, it is necessary to resort to methods which essentially count the number of gas molecules present i.e., it is the number density not the pressure which is measured. One of the most convenient methods to measure the number density is to use some technique to ionize the gas molecules and then collect the ions. The resulting ion current is directly related to pressure and a calibration can be performed. The probability of ionizing a gas molecule will depend on a variety of factors and hence, the ionization gauge will have different sensitivity values for different gas species. B6 1) For p < 1 mbar and T Gauge T Vacuum the linearity of a gauge with a controlled temperature is influenced by the thermal transpiration (gas type dependent) at the maximum in the same order of magnitude as the zero point stability. See K. F. Poulter, et al., Vacuum 33, 331 (1983); W. Jitschin and P. Ršhl, J. Vac. Sci. Technol. A, Vol. 5, No. 3, 1987. B6.3
Page 1: B6 Vacuum Gauges Vacuum Gauges and
Page 5 and 6: Transmitter Technology Vacuum Gauge
Page 7 and 8: SKY TM Capacitance Diaphragm Gauge
Page 13 and 14: Bayard-Alpert Pirani Gauge BPG400 V
Page 15 and 16: Pirani Standard Gauge Vacuum Gauges
Page 17 and 18: Pirani Standard Gauge Vacuum Gauges
Page 19 and 20: Bayard-Alpert Gauge Vacuum Gauges B
Page 21 and 22: Bayard-Alpert Gauge Vacuum Gauges T
Page 23 and 24: Penning Gauge PEG100 Vacuum Gauges
Page 25 and 26: Vacuum Gauge Controller VGC103 Vacu
Page 27 and 28: Vacuum Switch VSA100 Vacuum Gauges

INFICON CATALOG 2000-2001 - Schoonover, Inc.

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