8.1 Calibration of gas sensors

Transcription

1 8.1 Calibration of gas sensors! CAUTION! Calibration gas handling and precautions Observe safety regulation and accident prevention regulations when using or handling test gases. Use test gases in well-ventilated areas only. Calibration can only be performed with calibration gas of a known composition and concentration. Gas that has exceeded its certification date should not be used. For most accurate results, the value of the calibration gas should be between 75% to 125% of expected value. Required equipment: Calibration gas, non-reactive regulators, non-reactive/non-absorbing tubing, a by-pass vent for excess calibration gas, flow regulating needle valve. Example: Stainless Steel Flow Controlled Regulator with Overflow Vent Testo Calibration Kit w/ Regulator! CAUTION! Do not pressurize the analyzer greater than 12 H 2 O (0.5 PSI) with calibration gas as faulty readings and damage may occur. Use a bypass vent. testo inc. 40 White Lake Road, Sparta, NJ (800) Fax (862)

2 Hydrocarbons gas should be in a carrier of O 2 at 5% to facilitate calibration. Gases like NO 2 and SO 2 should only be used with non-reactive, nonabsorbent materials such as stainless steel, Teflon and C-Flex. Use single component gases to eliminate and/or identify cross interference. Calibration time should not need to exceed 5 minutes per gas exposure to reach stability (exception of old sensors and NO 2 and SO 2 which have slower response) Teflon tube Vent/flow indicator VENT 1-2 l /min Rotameter (Shows slight excess flow rate) High Pressure Calibration Gas Needle valve Analyzer Sample Probe Needle Valve To analyzer Calibration procedure Preparation (1) Ensure the analyzer is fully charged or operating on AC current (2) Ensure the ambient air is free from background gas contaminants. Warm-up (3) Start analyzer and operate pump for 15 minutes to purge residual gases from sensors and to fully achieve operating stability (4) Zero the analyzer by pressing the function key Zero (here the second on the left). (5) Press to enter the menu. 36 testo inc. 40 White Lake Road, Sparta, NJ (800) Fax (862)

3 (6) Press to highlight Sensors and press. (7) Highlight Calibrate and press. Example: CO Calibration (8) Select the sensor to calibrate with and (here CO) and press to accept. (9) Input the indicated value of the calibration gas (e.g. 100). testo inc. 40 White Lake Road, Sparta, NJ (800) Fax (862)

4 Connect to calibration gas (10) Connect the sample probe to the calibration apparatus. (11) Ensure the needle valve to the calibration gas is closed. (12) Press the Start function key. The total calibration gas flow will be approximately 2 liters/minute. 1 liter/minute to the analyzer; less than 1 liter/minute vented to assure adequate supply. Adjust gas flow (13) Start the flow of the calibration gas to the analyzer by adjusting the needle valve. (14) Carefully adjust the flow to provide 1-2 liters/minute flow through the bypass vent. (15) When the sensor reading indicates a change, time the process for 3-5 minutes and wait for the readings to stabalize. (16) During the calibration this screen appears and shows the values. Test Apply For a new adjustment of the analyzer! At the end of the 3-5 minutes, press the Apply function key to adjust the sensor. Then press Apply a second time and enter the Cal gas values to save the values into the memory. For checking the analyzer only! Selecting Test will save the values but not calibrate (adjust) the sensor. Escape will not calibrate (adjust) the sensor. Prepare to calibrate other sensors (17) Purge the analyzer on fresh air for 5 minutes before beginning the next gas Printing calibration data If there is no calibration data in the sensor (e.g. sensors with a manufacturing date before January 2003) dashes are printed instead of the target and actual values. Only the serial number and date of adjustment are printed. Calibration of CO dilution with calibration gas If you need high accuracy in CO dilution mode, the system can be calibrated. Call testo for details. 38 testo inc. 40 White Lake Road, Sparta, NJ (800) Fax (862)

5 8.2 CO-Measuring ranges with different dilution steps If the ambient air contains interfering gases, push the hose onto the dilution inlet ( ) next to the Trigger Input and place hose in a clean atmosphere. 1/x Possible dilution factors Dilution Ratio of diluting factor gas : measured gas 1 no dilution 2 1 : : : : : 1 Auto 5 : 1 when CO reaches 1000 ppm when H 2 reaches 1000 ppm Our recommended dilution factors when testing: Dilution factor CO concentration in flue gas with CO standard Dilution factor CO concentration in flue gas with CO low 1 0 to to to 2, to to 10, to 1, ,500 to 20, to 3, ,000 to 80, ,000 to 6, ,000 to 400, ,000 to 20,000 Technical data: Dilution Measuring range Resolution Measuring range Resolution factor with CO standard with CO low 0 0 to 10,000 ppm 1 ppm 0 to 500 ppm 0.1 ppm 2 0 to 20,000 ppm 2 ppm 300 to 2,000 ppm 0.2 ppm 5 0 to 50,000 ppm 5 ppm 500 to 10,000 ppm 0.5 ppm 10 0 to 100,000 ppm 10 ppm 1,500 to 20,000 ppm 1 ppm 20 0 to 200,000 ppm 20 ppm 3,000 to 80,000 ppm 2 ppm 40 0 to 400,000 ppm 40 ppm 6,000 to 400,000 ppm 4 ppm Calibrate dilution system every 6 5X. Put the analyzer in the 5X dilution mode and calibrate the CO sensor as normally performed. Examples of when to use the dilution system: when combustion source is out of tune or improperly controlled in reduced burner atmosphere adjustment of industrial burners (from high to low CO ) optimization and tuning of gas turbines engine measurement at high H 2 levels (controlled motors) during long-term measurements to keep a low load on the CO sensor testo inc. 40 White Lake Road, Sparta, NJ (800) Fax (862)