beta attenuation mass monitors a discussion of technology
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Beta Attenuation Mass Monitors A Discussion of Technology. Dennis Hart Met One Instruments, Inc. Overview. History of beta gauge technology Theory of operation Beta gauge advantages Beta gauge safety BAM-1020 technical overview E-BAM technical overview What’s next in beta technology

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Presentation Transcript
  • History of beta gauge technology
  • Theory of operation
  • Beta gauge advantages
  • Beta gauge safety
  • BAM-1020 technical overview
  • E-BAM technical overview
  • What’s next in beta technology
  • Conclusion
history of beta technology
History of Beta Technology
  • 1930s - Beta attenuation measurement technology first developed for industrial processes.
  • 1970s - Beta attenuation adapted to measure particulate by Sibata Scientific of Japan.
  • 1990s - BAM-1020 developed with reduced size and advanced microprocessor control.
  • 2002 - E-BAM developed for rapid field deployment and variable data intervals.
history of beta technology1
History of Beta Technology
  • Over 2,000 BAM-1020 units deployed.
  • Over 200 E-BAM units deployed.
theory of operation
Theory of Operation
  • Beta rays are measured through clean filter tape.
  • Air containing particulate is sampled and deposited on the filter tape.
  • Beta rays are measured through dirty filter tape.
  • The difference between the two measurements is proportional to the mass concentration.
beta gauge advantages
Beta Gauge Advantages
  • Time proven, stable technology: beta gauges have been in use for over 60 years.
  • Beta attenuation technique is simple, easy to use, and requires less maintenance than other methods.
  • Fewer site trips required, ideal for remote deployment.
  • Met One beta gauges are manufactured and supported from the United States.
beta gauge advantages1
Beta Gauge Advantages
  • Seasonal and geographical correction factors are not needed.
  • It is not necessary to calibrate the beta measurement system in the field.
  • BAMs provide excellent agreement with gravimetric reference standards when properly maintained and operated.
  • Beta technology is virtually unaffected by the chemical composition of the sampled particulate.
beta gauge safety
Beta Gauge Safety
  • The BAM-1020 and E-BAM each contain a small amount of 14C, a naturally occurring radioactive isotope of carbon.
  • Activity level of the 60 mCi 14C source is similar to a commercial smoke detector, and is licensed with the NRC under the same provisions.
  • Sources with activity under 100 mCi require no special government licensing to own.
  • Met One Instruments has an “Exempt Distribution License” from the US-NRC to distribute the beta sources.
beta gauge safety1
Beta Gauge Safety
  • Users are not required to take any specific precautions when handling the beta gauge.
  • USA customers do not require licensing to own a Met One beta gauge.
  • The end user will never need to remove, replace, or handle the beta source.
  • The unit may be returned to the factory for disposal at the end if its service life, although this is not required.
bam 1020 advantages
BAM-1020 Advantages
  • Continuously samples and measures ambient air for particulate matter.
  • Designed to predict the mass concentration measured by manual gravimetric samplers with the highest accuracy.
  • Does not require the use of correction factors
bam 1020 advantages1
BAM-1020 Advantages
  • 60 day continuous operation between filter tape changes.
  • Designed for long term operation at a fixed installation.
  • Powerful integrated 6 channel data logger compatible with a wide array of meteorological sensors.
  • Best accuracy of all beta models.
us epa equivalent method
US-EPA Equivalent Method
  • Met One BAM-1020 is the ONLY US-EPA designated beta gauge currently manufactured.
  • EQPM-0798-122
  • Equivalency for PM10 measurement
simplicity flow system
Simplicity – Flow System
  • The BAM-1020 airflow system consists of a few simple components:
    • Inlet/Nozzle
    • Temp/RH/BP sensors
    • Debris filter
    • Mass flow sensor
    • Flow controller
    • Pump (external)
simplicity measurement system
Simplicity – Measurement System
  • The BAM-1020 measurement system consists of a few simple components:
    • Carbon 14 Beta source
    • Filter tape support
    • Photomultiplier tube detector
    • Preamp circuitry
critical checks
Critical Checks
  • The flow system should be calibrated or verified on a regular basis.
  • A leak check is performed with every flow calibration.
  • The nozzle sealing surface and support vane may need to be cleaned more frequently in humid environments.
critical checks1
Critical Checks
  • The nozzle seal against the filter tape is important for proper airflow regulation.
  • The nozzle and support vane need to be cleaned at least as often as the filter tape is changed.
bam 1020 calibration
BAM-1020 Calibration
  • Calibration occurs once at the factory against a transfer standard in a smoke room chamber.
  • There are no environmental correction factors that need to be employed.
  • Zero and Span are checked once per hour during operation. No changes are made however.
e bam advantages
E-BAM Advantages
  • Rapid deployment, portable unit.
  • DC operation for batteries or solar arrays.
  • All weather construction.
  • Easy set up: may be mounted on tripod or existing structure.
  • Compatible with optional wind sensors for smoke tracking.
  • Instrument operating temperature between -30° and +40° C.
e bam advantages1
E-BAM Advantages
  • “As needed” filter tape advance. One roll of tape may last up to a year depending on concentration levels.
  • Real-time data capability due to simultaneous sampling and measurement.
  • Concentration can be calculated on a 5, 15, 30, or 60 minute basis. Higher time resolution than the BAM-1020 is possible.
  • Up to 200 days of data storage, depending on data storage rate.
e bam advantages2
E-BAM Advantages
  • Lower cost and less parts.
  • AirSys satellite communications available for remote data retrieval.
  • Replaceable integral air pump.
mass calculation1
Mass Calculation
    • I0– beta measurement across clean filter
    • I – beta ray measurement across dirty filter
    •  – calibration coefficient (m2/g)
    • x – mass density on filter tape (g/m2)
    • A – dust spot deposition area on filter tape (m2 )
    • V – sampled volume (m3)
    • C – particulate matter concentration (g/m3)
how performance is measured
How Performance is Measured
  • Accuracy
    • Percentage deviation from 24-hour gravimetric Reference Standard
    • Beta technology has superior 24 hour accuracy compared to other methods.
  • Precision
    • Repeatability of a single measurement.
  • Stability
measurement challenges
Measurement Challenges
  • Environmental conditions can play a role in the accuracy of beta attenuation measurements. The two main factors are:
    • Air temperature
    • Relative humidity and moisture.
measurement challenges1
Measurement Challenges
  • Temperature:
    • The BAM-1020 must be in a temperature controlled environment.
    • The temperature of the air flow in the E-BAM is measured and automatically compensated.
measurement challenges2
Measurement Challenges
  • Humidity:
    • Moisture accumulation on the sample spot may be measures as mass.
    • BAM-1020 and E-BAM use smart heater technology to lower the RH of incoming air.
    • Mild heat and hourly spot changes virtually preclude effects on VOCs.
    • Either unit may be operated at ambient conditions if desired.
what s next in beta technology
What’s Next in Beta Technology
  • Detector sensitivity and noise improvements.
  • New pump options for E-BAM.
  • Advances temperature correction algorithms.
  • Advanced filter tape materials.
    • Less affect on concentration measurement.
    • Tests ongoing to improve nozzle leaks with thinner material.
    • Studies underway for maximum concentration levels.
  • Met One Instruments is constantly testing and experimenting to improve the beta gauge product line.
  • BAM-1020 exhibits documented superior performance to other beta gauges.
  • We welcome suggestions for future improvements.
  • Applications/Sales: David Gobeli, Ph.D.
  • Science: Herbert Schloesser, Ph.D.
  • Service: Mike Putnam, Service Mgr.
  • (541) 471-7111