454 Commissioning/Decommissioning4.7.1.2 Performing an offset calibration to ambient airNOTICEThe probe must be removed or ambient air must be ensured at the measuring point.• Trigger offset calibration alternatively by:– Display and operating unit by the [cal] menu– Remote Display Software by the [cal] menu– Multifunction key (only with ambient air) see chapter 4.7.1 Measurement with LS2-K Ifthe system works properly for 20 Min. after finishing the offset calibration repeat thecalibrationMenu functionPressing the [cal] menu key shows ’Start calibration’ in the display. After the activation of thecalibration 4 functions are available (see chapter 4.7.1.3 Performing an Offset Calibration withCompressed Air), Use the two upper functions for offset calibration:• Start offset calibration in ambient air• Start offset calibration with compressed air (open stopcock in PCB)• Start calibration with reference measurement• Start calibration with test gas (open stopcock in PCB)Press cursor keys up/down to select the required offset calibration.Press ENTER key to start the selected offset calibration.Use the menu function ’ Break calibration before end!’ to abort the calibration.After finishing the automatic calibration procedure in ambient air the LT2 changes to MEAS-UREMENT mode.Press the [exit] key to change to the indication of the measurement values.By multi function key T2 as an alternative (with ambient air only):Fig. 4-19 Internal view of probe connection box LS2-K1 Differential pressure sensor2 Absolute pressure sensor3 Throttle for calibration gas4 Throttle for reference air5 Stopcock for calibration gas6 Hose connection for test gas (instrument air ortest gas ca. 0.3 bar)7 Outlet for air8 Hose connection for reference air (instrumentair ca. 0.3 bar)9 Electrical connection probe to LT2-K10 Electrical connection absolute pressure sen-sor to LT2 analogue input 211 Electrical connection differential pressure sen-sor to LT2 analogue input 1
