TM 10-6665-297-13&P3-2CALIBRATION(continued)3-2.2CalibratingaSystemwithTwoDetectorsperCD800/830ControlUnit. (continued)5.Turn screw adjustment of ZERO potentiometer R24 on control module printed circuit board to setmeter indicator to zero on meter scale.6.If meter indicator cannot be set to zero, disconnect detector 2 at the control module and install a setof 15-ohm resistors across DET 2 A-C-R terminals. If meter indicator can not be adjusted to zerowith one operating detector, probably the response characteristics of the paired sensor elements aretoo dissimiliar while both are operating. (One element may have been long in use and the othernew.)7.If necessary, replace old sensor element, reconnect detector 2 to control module, and adjust ZEROpotentiometer R24 to set meter indicator to zero on meter scale.After meter indicator has been set to zero, calibrate paired detectors to co-ordinate meter indicatorpercent L. E. L. deflection range with detector response to gas as follows:1.Apply sample gas of known concentration from J-W gas calibration cylinder or ProfessionalCalibration Kit 51-7070 to one detector. Second detector must be simultaneously sampling zerocombustible gas.2.Turn adjustment screw of GAIN potentiometer R10 on control module circuit board until meterreading matches percent L. E. L. concentration of gas specified on sample gas cylinder label orproduced by Professional Calibration Kit 51-7070.3.Remove sample gas from first detector. Confirm that meter returns to zero in response to fresh air.Expose second detector to sample gas. Compare meter reading with first reading taken. Do notreadjust GAIN control R10. If readings differ more than 10 percent of the L. E. L. reading, replacesensor element in detector with lowest reading and repeat ZERO and GAIN adjustment procedures,following steps 1 and 2 above.23-96174/14/773-8
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