Monitoring Systems

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Monitoring Systems
Gaseous Pollutants mini-course TAMS Center
February 2009
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Can Be Simple
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Temp Sensor
Source CTUIR Ozone QAPP
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Can Be More Complex
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Cherokee Nation Ambient Air Monitoring
Meteorological
FRM PM 2.5 Sampler (Filter Based)
Air Quality Monitoring Shelter
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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
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The First Rule Make everything at the
monitoring site as easy to get to as possible. If
its hard, the quality of your data may suffer.
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Whats 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
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Possible water trap
Use FEP (clear) ¼ inch Outside Diameter tubing.
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
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Residence time must be less than 20 seconds and
should be less than 10 seconds
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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 EPAs
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.
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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
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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
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• 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

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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
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Caution warm moist air may condense when inside
an air conditioned shelter.
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Anemometer measures wind speed
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Calibration System Dont 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
EPA Protocol Gas Most have 2-year certification
Exhaust manifold
Insect screen
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Source CTUIR Ozone QAPP
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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 concentrations 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.
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20 to 30 degrees Celsius
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Probe Siting
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2X Difference in height
Difference in height
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Obstacle
270 degrees must be open at 30 degrees from
horizontal
1/3 of 90 degrees
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Datalogger and data flow
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Graphic Courtesy of U.S. EPA Office of Air
Quality Planning and Standards -Nealson Watkins
Lewis Weinstock
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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

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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
Voltage
PPM
PPM
Change is proportional
Full Scale
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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
Voltage
PPM
PPM
Full Scale
Change is proportional
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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 its 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
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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
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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

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Analog Examples
ESC
Where is the wire connected?
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Datalogger analog in
Analog outputs on API Teledyne NOx analyzer NOx,
NO2, NO, Status
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Analog Examples
Campbell
Multiplier
Volt range
PPB Range 500 Volts 5000 mV
500
0.1
Where is the wire connected?
5000
UNITS !!!
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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)
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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
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• 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?

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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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More offset examplesWhere is the low end of the
instrument range in relation to 0?
0
50 ºC
-50 ºC
Range 100 ºC Low end of range -50 Offset
-50
Temperature ºC
28
32
Rang 4 of Hg Low end of Range 28 Offset
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Barometric Pressure
500 ppb
Range 500ppb Low end of range 0 Offset 0
Ozone
0
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Contrasting Digital vs. Analog Connectivity
Analog Established method using ranged line
voltage across a connection to track a single
data type.

• In high sensitivity precursor gas applications,
  signal exists at bottom of usable voltage range
  and data stream may be affected by noise.
• D/A range may be limited to 10 bit (1024 steps)
  in some cases (TEI-C series).
• D/A calibrations may be required to match
  analyzer output to data logger input readings.
• Many instruments have limited analog-out
  capability, restricting availability of
  diagnostic data (e.g., RP TEOM has only 3 analog
  outputs).
• Acquiring auxiliary data requires additional
  wiring creating opportunities for loose or broken
  physical connections.

Analog Connection
Slide Courtesy of U.S. EPA Office of Air Quality
Planning and Standards -Nealson Watkins Lewis
Weinstock
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Contrasting Digital vs. Analog Connectivity
Digital Uses connection such as RS-232 to track
and log all available monitor information.

• Multiple data types can stream across single
  connection.
• Nearly unlimited diagnostic retrieval capability.
• No risk of data corruption due to analog noise at
  very small voltage signal levels or due to ground
  loop effects.
• A/D calibrations not required.
• Addressable monitors can be individually
  interrogated and multi-dropped to reduce wiring.
• Additional flexibility in tracking over-range
  conditions where analog signal pegs.
• Digital systems sensitive to changes in
  instrument firmware and output formats!

Digital Connection
Slide Courtesy of U.S. EPA Office of Air Quality
Planning and Standards -Nealson Watkins Lewis
Weinstock
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Envidas for Windows (EFW)
Digital I/O Relay Control

• PC based system (no logger required).
• 64 available channels for analog or digital
  inputs.
• Access via serial, digital I/O, analog I/O, or
  other data loggers.
• Standard configurations facilitate digital
  connectivity with commercially available
  monitors.
• Real-time data, on the fly corrections, data
  validation, alarms, diagnostics.
• Multi-site, remote command and control capable
  (over TCP/IP).
• Easily configurable for internet-based polling
  via broad-band.
• Capability to emulate a data logger allows its
  insertion into existing data acquisition network.

Slide Courtesy of U.S. EPA Office of Air Quality
Planning and Standards -Nealson Watkins Lewis
Weinstock
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AQS File for SO2
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Tire chains Practical bag
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