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www.thinkSRS.com 1 Gas Correction Curves for PG105 Gauges It is important to understand that the pressure indicated by a PG105 convection-enhanced Pirani gauge depends on the type of gas. All PG105 convection-enhanced Pirani gauges are factory-calibrated and temperature-compensated for nitrogen (air). However the response of the gauge to other gases is very well characterized and, with the proper calibration data, it is possible to obtain accurate pressure measurements for other gases as well. IGC100 controllers are factory-loaded with Nitrogen and Argon specific calibration curves compatible with all PG105 gauges, and direct pressure measurements are possible for both gases. If you must measure the pressure of gases other than Nitrogen or Argon, use Gas Correction Curves, like figures I-1 and I-2 included in this application note, to convert "nitrogen equivalent pressure" readings into "actual pressure" readings for those gases. Gas Correction Factors (relative to nitrogen equivalent readings) can also be used for pressure measurements below 1 Torr (See Table I-1) PG105 users should generate their own conversion curves for gases, or mixtures of gases, not included in this application note. A calibrated, gas-independent, capacitance manometer is recommended as a transfer standard1. In This Application Note Gas Correction Curves and Factors 3 Nominal Gas Correction Factors for Figures I-1 and I-2. 4 Overpressure risks 5 References 6 (408)744-9040 Stanford Research Systems www.thinkSRS.com 2 Gas Correction Curves for PG105 Gauges Stanford Research Systems (408)744-9040 www.thinkSRS.com Gas Correction Curves for PG105 Gauges 3 Gas Correction Curves and Factors Important The conversion curves and factors listed in this application note only apply 1. when the pressure readings displayed by the controller are based on the nitrogen calibration curve (i.e. PG Cal Curve = N2 Curve) 2. the gauge tube is mounted with its axis horizontal. N2 Pressure Reading (Torr) 0.001 0.01 0.1 1 Actual Pressure (Torr)