Aalborg DFM 26 Operating Manual
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Contents
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31analog output calibration only), an insulated (plastic) screwdriver, a flow regulator(for example - metering needle valve) installed upstream from the Mass FlowMeter and a pressure regulated source of dry filtered nitrogen gas (or other suit-able reference gas). It is recommended to use Aalborg7 supplied calibration andmaintenance software to simplify the calibration process. Gas and ambient tem-perature, as well as inlet and outlet pressure conditions should be set up in accor-dance with actual operating conditions.7.2 Gas Flow Calibration of DFM Mass Flow MetersAll adjustments in this section are made from the outside of the metervia digital communication interface between a PC (terminal) and DFM.There is no need to disassemble any part of the instrument orperform internal PCB component (potentiometers) adjustment.DFM Mass Flow Meters may be field recalibrated/checked for the same range theywere originally factory calibrated for. When linearity adjustment is needed, or flowrange changes are being made proceed to step 7.2.3. Flow range changes mayrequire a different Restrictor Flow Element (RFE). Consult your distributor orAalborg7 for more information.7.2.1 Connections and Initial Warm UpPower up the Mass Flow Meter for at least 30 minutes prior to commencing thecalibration procedure. Establish digital RS-485/RS-232 communication betweenPC (communication terminal) and the DFM. Start Aalborg7 supplied calibrationand maintenance software on the PC.7.2.2 ZERO Check/AdjustmentCheck SENSOR AVERAGE counts on the DFM LCD status line. Keep pressing the(p) [Up] button from the main screen until status line will display Device SensorAverage ADC counts. With no flow conditions the sensor Average reading must bein the range 120 10 counts. If it is not, perform Auto Zero procedure (see sec-tion 5.3.10 "Zero Calibration").7.2.3 Gas Linearization Table AdjustmentNote: Your DFM Digital Mass Flow Meter was calibrated at thefactory for the specified gas and full scale flow range (see devicefront label). There is no need to adjust the gas linearization tableunless linearity adjustment is needed, flow range has to be changed,or new additional calibration is required.Any alteration of the gas linearization table will void calibrationwarranty supplied with instrument!,, |
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