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Monitoring Systems

Monitoring Systems. Gaseous Pollutants mini-course TAMS Center February 2009. Can Be Simple. Temp Sensor. Source: CTUIR Ozone QAPP. Can Be More Complex. Cherokee Nation Ambient Air Monitoring. Meteorological. FRM PM 2.5 Sampler (Filter Based). Air Quality Monitoring Shelter.

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Monitoring Systems

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  1. Monitoring Systems Gaseous Pollutants mini-course TAMS Center February 2009

  2. Can Be Simple

  3. Temp Sensor Source: CTUIR Ozone QAPP

  4. Can Be More Complex

  5. Cherokee Nation Ambient Air Monitoring Meteorological FRM PM 2.5 Sampler (Filter Based) Air Quality Monitoring Shelter

  6. Inside the Monitoring Shelter Vertical manifold Tubing for NOy Gas Analyzer Rack Toxics Flow Controller NOy Data Logger Continuous Particulate Sensor Unit NOx Calibrator SO2 Continuous Particulate Monitor Control Units Ozone Zero Air Generator

  7. The First Rule: Make everything at the monitoring site as easy to get to as possible. If it’s hard, the quality of your data may suffer.

  8. What’s materials are allowed? Teflon and borosilicate glass (Pyrex) Types of Teflon: PTFE, FEP, PFA Compression Union Stopcock Cap Nut (seal) Compression Union Tee Compression Union Reducer Ferrule nut Compression to NPT adapter

  9. Possible water trap Use FEP (clear) ¼ inch Outside Diametertubing. Typical inside diameters are 1/8, 5/32 and 3/16. 1/8 inch ID can restrict flow (1/8 = 0.125) (thick wall) 5/32 is middle ground (5/32 = 0.156) 3/16 inch ID kinks easily (3/16 = 0.186) (thin wall) http://www.savillex.com/catalog/index.php

  10. Residence time must be less than 20 seconds and should be less than 10 seconds

  11. The residence time section of the CTUIR Ozone QAPP In order to collect air for analysis at the minimum required 3-meter height from ground level, the air entering the analyzer must be captured and moved to the analyzer without causing any condition that will change the composition of the sample air. All components of the sample collection system that contacts sample air will be made of Pyrex glass or Teflon to minimize the potential for reaction once air enters the system. Also, all components in the sample collection system will be replaced or cleaned at least quarterly. Residence time, the time from when air enters the system until it enters the analyzer, will be kept below EPA’s maximum recommended 10 seconds (EPA requires residence time not to exceed 20 seconds). CTUIR will use 5/32 inch inside diameter and 1/4 inch outside diameter Teflon tubing as the intake probe. The maximum tubing length at the maximum 10 second residence time is calculated as follows.

  12. To calculate the maximum total system collection volume in liters while achieving a 10-second residence time when flow is 0.5 liters per minute 0.5 Liters per minute * (1 minute/60 seconds) = 0.00833 liters per second 0.00833 liters per second * 10 seconds = 0.0833 liters To calculate volume in liters per foot of tubing 5/32 inches (tubing inside diameter) = 0.15625 inches = 0.01302 feet Area of tubing opening = 3.1416 * (0.01302/2)2 = 0.0001331 square feet 0.0001331 square feet = 0.0001331 cubic feet in 1-foot of tubing length. 0.0001331 ft3 * (28.31685 liters / 1 ft3) = 0.003769 liters of volume per foot of 5/32 ID tubing Water Trap Since the air may be cooled in the climate controlled enclosure and this process may condense moisture, and/or rain may enter the sample collection system under extreme conditions, a water trap may be needed to protect the equipment. CTUIR will use a glass water trap no larger than 25ml (.025 liters). Source: CTUIR Ozone QAPP

  13. Maximum tubing length Max tubing volume = (Maximum allowed total intake system volume) - (volume of water trap) 0.0833 liters - 0.025 liters = 0.0583 liters Maximum tubing length in feet = (max tubing volume) / (tubing volume per foot) 0.0583 liters / (.003769 liters/foot) = 15.47 feet of tubing To ensure an acceptable residence time CTUIR will limit the 5/32-inch ID tubing length to 15 feet or less and will not exceed 25ml volume in the water trap. Source: CTUIR Ozone QAPP

  14. In this instance we wanted to know the maximum length of tubing we could use and still maintain a 10 second residence time at a flow rate of 0.5 liters per minute if we put a 25ml water trap in the line. • So, what did we do? • We determined the maximum volume of air the analyzer would use in 10 seconds. • We calculated the volume in 1 foot of our tubing (V = pi * (d/2)2 * L) • We subtracted the water trap volume from the maximum volume in step 1 • Then we divided the remaining volume from step 3 by the volume per foot of tubing • The rest was just getting things into the same units

  15. Water trap and long line ¼-Inch Teflon tubing Need a longer line? Use a small pump to decrease residence time Small Pump Teflon Compression Tee Ozone Analyzer

  16. Caution: warm moist air may condense when inside an air conditioned shelter.

  17. Anemometer measures wind speed

  18. Calibration System Don’t pressurize analyzers; you must vent. Total flow from calibrator must exceed combined analyzer demand Wall Zero Air Vent Calibrator Regulator (2 stage stainless steel match fittings & purge CGA 660) Cal gas must pass through filter Analyzer Analyzer Analyzer Cal Bottle EPA Protocol Gas Most have 2-year certification Exhaust manifold Insect screen

  19. Source: CTUIR Ozone QAPP

  20. Each monitoring organization must have at least one Local Primary Standard which serves as the point of traceability (comparison) for each ozone analyzer used by that monitoring organization. The LPS must include an ozone generator, an output port or manifold, an UV photometer and a zero air source, and must be verified to be within limits of the average of six comparisons between it and the EPA SRP, and the result of each concentration’s comparison must be less than + 4% (relative percent difference) AND + 4 ppb. The Local Primary Standard can be used for routine verifications (span checks) of local equipment as long as the requirements for the LPS are met, including the restriction that the LPS never measures ambient air, etc. However, audits must be performed with a system that is two levels of authority removed from the LPS; e.g., the LPS is calibrated to the EPA SRP, and the audit equipment is verified against a DIFFERENT EPA SRP.

  21. 20 to 30 degrees Celsius

  22. Probe Siting

  23. 2X Difference in height Difference in height

  24. Obstacle 270 degrees must be open at 30 degrees from horizontal 1/3 of 90 degrees

  25. Datalogger and data flow

  26. Graphic Courtesy of U.S. EPA Office of Air Quality Planning and Standards -Nealson Watkins & Lewis Weinstock

  27. Common Types of Datalogger Communication • Analog • Instrument outputs a voltage • Datalogger senses voltage • Both must know what the voltage represents • The range of voltage used, and the concentration range of the instrument must be coordinated between the datalogger and the instrument • Digital • Direct communication – data streams • Compatibility and connection/communication parameters • Current • Instrument outputs current • Current is passed through a close tolerance resistor • Datalogger senses voltage drop across the resistor

  28. Basic Analog Concept If 10 volts = 0.500 ppm Then 5 volts = 0.250 ppm 0.500 ppm 10 Volts 5 Volts 0.250 ppm Voltage PPM Voltage PPM Change is proportional Full Scale

  29. Basic Analog Concept If 10 volts = 0.500 ppm Then 1 volt = 0.050 ppm 0.500 ppm 10 Volts 1 Volt 0.050 ppm Voltage PPM Voltage PPM Full Scale Change is proportional

  30. Multiplier Full range of analyzer/sensor = Multiplier Full range of voltage Example: An ozone analyzer is set to a full scale of 0.500 ppm, and it’s analog output is set to a full scale of 2.5 volts 0.500 ppm = 0.2 ppm / volt 2.5 volts If the datalogger sees a voltage of 0.67 it will have to multiply the voltage by the multiplier to get the concentration 0.67 volts X 0.2 ppm/volt = 0.134 ppm

  31. Analog Example 0.67 volt 0.67 volt 0.134 ppm 0.134 ppm Full Scale 0.500 PPM 2.5 Volts Datalogger Monitor Converts the voltage to a digital concentration and logs it Converts digital concentration to a voltage output Multiplier = 0.500 ppm / 2.5 volts = 0.2 ppm / volt 0.2 ppm/volt X 0.67 volt = 0.134 ppm .134 ppm / 0.500 ppm = 0.268 0.268 x 2.5 volts = 0.67 volts

  32. Datalogger Configuration Differences • Some dataloggers need a multiplier and an offset for configuration • ESC asks for: • Volts High Input • Volts Low Input • High Output E.U.s • Low Output E.U.s And then calculates multiplier and offset

  33. Analog Examples ESC Where is the wire connected?

  34. Datalogger analog in Analog outputs on API Teledyne NOx analyzer NOx, NO2, NO, Status

  35. Analog Examples Campbell Multiplier Volt range PPB Range 500 Volts 5000 mV 500 = 0.1 Where is the wire connected? 5000 UNITS !!!

  36. Single Ended & Differential Voltage(Campbell Scientific – SE & DIFF) Sensor Sensor .1 Volt (L) 2.5 Volts (H) 2.5 Volts 2.5 Volts Datalogger 2.4 Volts Datalogger Single Ended measures between SE terminal and ground Ground Differential measures between two voltages SE 2 1 (Single ended channel 2) 1 Diff (Differential Channel 1) L H (Screw on datalogger)

  37. Zeno has A, B and C in their configuration.A is for non-linear instruments (not used here) B is the multiplier C is the offset

  38. Offsets • Think of the range of the instrument • -50º C to +50º C • 223º Kelvin to 323º Kelvin • 0 ppm to 0.500 ppm • Then think: Where is the low end of the range in relation to 0?

  39. Offset examples • A barometric pressure sensor has a range from 26 to 32 inches of mercury • This is an offset of +26 • An ozone analyzer senses ozone between 0 and 500 ppb • This is an offset of 0

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