Molecules have to collide many times before they reach the outer body of the sensor (the thermal sink). However, the heat removal becomes non-linear as the pressure is further increased into the viscous flow regime, where gas-gas collision can reorient molecules back towards the heated wire. Just as with the thermocouple gauges, thermal conductivity by molecular collisions increases linearly with pressure over the 0.001 to 1 Torr pressure range. The vacuum pressure is therefore calculated from the pressure induced imbalance in the Wheatstone bridge circuit. As the vacuum pressure increases, gas molecules transport heat away from the filament, and the resistance of the pressure sensor will move to a lower value which unbalances the circuit. A Pirani gauge is designed to measure the resistance imbalance where the heated filament forms one of the arms of a Wheatstone bridge circuit. Pirani vacuum gauges can be classified as a thermal conductivity gauge being very similar to the thermocouple gauge where the resistance of the heated wire is measured to determine vacuum pressure. Adjustable set point for simple process control and interlockingīackground On Pirani and Convection Enhanced Pirani Gauges.Easy Access to signal cable with compact enclosure.For any other gas type a conversion is required in order to obtain the correct pressure reading, common gases: nitrogen, argon, carbon dioxide, helium, krypton and neon. The APG MP is calibrated for use in nitrogen, and will read correctly with dry air, oxygen and carbon monoxide. Edwards recommends mounting the gauge tube vertical in order to minimize the build up of process particulates and condensable vapors within the gauge. For correct pressure indication in your chosen gauge orientation, the gauge should be recalibrated at atmospheric pressure. The APG-MP can be mounted in any orientation however the gauge tubes are individually factory calibrated in nitrogen whilst vertical. If you connected the APG to your own controlĮquipment, use the procedure on page 22 of the manual.pdf below. If you connected the APG to a Edwards AGC controller orĪGD display, use the set-point adjustment procedureĭetailed in the instruction manual supplied with the These Edwards APG-MP Active Pirani vacuum gauges has a KF16 NW16 vacuum flange are new with Edwards part number D02185000. This gague contains a Platinum / rhodium (90/10) filament and can measure pressure down to 10-3 Torr and is stainless steel. The instruction manual for these Edwards APG-MP series gauges is available in PDF format below. The signal cables and TIC vacuum gauge controllers are sold separately. They measure pressure from 1000 down to 10 -3 Torr. They are also CSA, C/US approved as well as fully RoHS compliant due to their lead-free construction. The new Edwards gauges are compatible with all Edwards TIC, ADC, TAG instrument controllers and other active gauge controllers and displays.
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