Frequently Asked Questions

Introduction

What is a microAeth?

The microAeth® Family has four models of microAeth®. All four microAeth AE51, MA200, MA300, and MA350 are self-contained analytical instruments, providing real-time Black Carbon analysis using the Aethalometer® technique. The instruments measure the rate of change in absorption of transmitted light due to continuous collection of aerosol deposits on a filter. This microAeth compare chart can help show how the instruments differ.

How does a microAeth measure Black Carbon?

An internal pump and mass flow controller draw an air sample onto a filter. A light source illuminates the filter and optical detector measures the rate of change of attenuation due to the absorbance of transmitted light by particles that are continuously collected on the filter. Measurement of absorbance at a wavelength of 880 nm is interpreted as concentration of Black Carbon (‘BC’). An internal lithium-ion battery and onboard data storage allow for continuous in situ collection of BC data.

Can a microAeth measure more than just Black Carbon?

Yes. The microAeth MA Series instruments (MA200, MA300, and MA350) are portable scientific instruments which measure the mass concentration of light absorbing carbon particles. The instruments have 5 analytical channels each operating at a different wavelength (880 nm, 625 nm, 528 nm, 470 nm, 375 nm). Measurement at 880 nm interpreted as concentration of Black Carbon (‘BC’). Measurement at 375 nm interpreted as Ultraviolet Particulate Matter (‘UVPM’) indicative of woodsmoke, tobacco, and biomass burning.

The microAeth MA200, MA300, and MA350 not only measure particles but have additional sensors that help you better understand the environment in which you are sampling and measuring. The microAeth MA Series instruments have internal sensors for measuring the relative humidity and temperature of the sample air stream. They also have internal sensors for measuring the altitude, pressure, location, and motion of the instrument.

The microAeth AE51 only measures absorbance at a wavelength of 880 nm and therefore is only able to interpret the concentration of Black Carbon (‘BC’).

Are all the features of the microAeth MA200, MA300, and MA350 currently available?

No. Most features are currently available but a few features are being released throughout 2017 and the release schedule is shown in the MA200 features roadmap, MA300 features roadmap, and MA350 features roadmap. All microAeth MA series instruments come with all hardware installed to support all features. Features that are not yet available, will become available through free firmware and microAeth Manager desktop client app updates that can be downloaded through the AethLabs website and implemented by customers, AethLabs or authorized service providers. Instruments will have to be returned to AethLabs in order to make wireless features available in the future.

What is the difference between the microAeth AE51 and the new microAeth MA Series MA200, MA300, and MA350?

The microAeth MA Series instruments have a number of important advancements beyond the microAeth AE51. The microAeth MA Series feature miniature cartridges that have a spool of filter material for particulate collection and on-board analysis. The MA200, MA300, and MA350 automatically control the advancement of the tape material, moving to a new unused spot when required while a user of the AE51 must manually replace a filter strip that contains only 1 sampling location. This allows the MA Series instruments to run continuously for multiple weeks or months without human intervention. The 5 wavelength optical engine in the MA Series instruments enables discrimination between organic and elemental particles which is helpful in source identification when measuring different aerosols. The MA Series also features the DualSpot® loading compensation method, which in real-time measures and adjusts for differing optical properties of particles of varying age and composition. The MA Series instruments also have built in GPS, Bluetooth, and Wi-Fi while also containing a number of additional sensors allowing for a better understanding of the sampling environment. There are many other differences which are shown in this microAeth compare chart.

What is the DualSpot loading compensation method?

The microAeth MA Series instruments include hardware and firmware that implement the patented DualSpot® loading compensation method. This method simultaneously collects aerosol samples on two analysis spots in parallel and at different face velocities while measuring the rate of change in absorption of transmitted light due to the particles loading on the filter. The DualSpot® loading compensation method is able in real-time to measure and adjust for differing optical properties of particles of varying age and composition. The use of the DualSpot® loading compensation method in the MA Series instruments is an optional user selectable feature.

Using microAeth instruments

Where can I use the microAeth?

The small size and lightweight of the microAeth® instruments enable the measurement of aerosol Black Carbon in a wide range of operating scenarios, not always possible using larger instruments. Utilizing the instrument’s flow rate and timebase settings, a wide range of concentrations can be analyzed. The AE51, MA200, MA300, and MA350 have been used as both a mobile and stationary monitor in numerous research applications. The instruments have been used in numerous research areas such as epidemiological / area monitoring, personal exposure assessment and environmental and transport emissions studies. The devices, especially the AE51 and MA200 have also been integrated into custom monitoring packages for atmospheric profiling on balloons, drones and other aircraft. Please refer to the AE51 Quick Start Guide and AE51 Operating Manual or MA Series Operating Manual for recommendations for best use practices.

What instrument settings should I use?

It is important to use the appropriate instrument settings for your sampling campaign. Optimal settings depend on the expected BC concentrations of the environment, and the temporal, spatial and sensitivity requirements of your study. Recommended settings for different scenarios can be found in the table on page 3 of the AE51 Quick Start Guide, page 10 of the AE51 Operating Manual, page 19 of the MA Series Operating Manual.

Should I use tubing connected to the inlet port of my instrument?

Yes. It is always recommended to use the sampling tube assembly supplied with your microAeth, screwed into the instrument's inlet port. Using this sampling tube assembly allows for more targeted sampling, can provide basic protection to the instrument inlet, and prevents the possibility of light leakage into the instrument's sample chamber.

Using microAeth AE51

How often do I need to change the filter strip in the microAeth AE51?

Filter life depends on the BC concentrations you are measuring, the flow rate settings of the instrument, and the duration of the sampling event. These three variables contribute proportionally to the rate of loading of particulate matter on the filter. Once the filter is saturated, the data being collected are no longer useful, so it is important to know when a clean filter needs to be installed. Filter saturation occurs when the total change in attenuation (ΔATN) of sampling on a filter strip is approximately 100. In order to ensure good data quality, however, AethLabs recommends changing filters more often than that. The instrument's red led indicator will blink as a general indicator of filter saturation. A guide for measurement limits regarding saturation can be found on the AE51 Specifications Sheet. For example, filters need to be changed according to the following BC concentration/flow rate ranges:

  • Avg. 5 µg BC/m3 for 24 hours @ 100 ml/min
  • Avg. 100 µg BC/m3 for 3 hours @ 50 ml/min
  • Avg. 1 mg BC/m3 for 15 minutes @ 50 ml/min

It will be necessary to change filters according to the sampling conditions and the instrument settings used. Using the first example listed above, measuring average concentrations of 5 µg BC/m3 at 100ml/min yields filter life of up to 24 hours. If the flow rate is reduced by a factor of 2 to the 50ml/min setting, the instrument can then operate for up to ~48 hours starting with a fresh filter. These BC concentration thresholds are the absolute maximums before a filter change is necessary, however, and AethLabs recommends you change filters more often.

As another example, if the the 1-second timebase is selected, and assuming instrumental noise on the order of +/- 4µg/m3, if the average concentration of BC is ~1µg/m3 then the instrumental noise will cause fluctuations between positive and negative values with excursions of ~ +5µg/m3 and -3µg/m3 respectively. Within the noise the signal does exist but the data must be smoothed for a longer period of time in order to resolve it. These positive and negative excursions due to instrumental noise will average out to the BC value. Additionally if measuring high concentrations of say 50µg/m3 with the same settings, the instrumental noise will remain unchanged, yet the signal (50µg/m3) to noise (+/-4 µg/m3) ratio is much improved and the variation in the data due to noise is less noticeable, and in this case always positive (50µg/m3 +/-4µg/m3). AE51 users can always upload their data file to our server and use our post-processing tools to smooth their data. There are a few different algorithms available for data smoothing. Register for a Dashboard account here

Do I need to turn the AE51 off before changing the filter?

Yes, always! The filter protects the pump from contamination. When the instrument is off, the pump is not spinning and it is safe to change the filter. Additionally, the light sources calibrate only when the instrument starts up, so you could end up with an optically saturated filter and invalid data if you do not shut the instrument off before changing a filter.

Do I need to save the AE51 filter strip after a sampling event?

No. Because the AE51 analyzes and internally records data in real-time, you do not need to save the filter strip for further analysis.

Can I use the AE51 filter strip for other types of laboratory analyses?

The filter strip used in the AE51 may be suitable for subsequent analyses. The method and equipment must have sufficient sensitivity to analyze the small loading of material on the AE51’s collection spot. In addition, the filter material may have background contamination due to material impurities, so blank measurements must be carried out in advance to determine if the analyte of interest can be detected.

Do all the microAeth use the same filters?

No. The microAeth AE51 uses a T60 Teflon-coated borosilicate glass fiber filter strip which has 1 sampling location and must be manually replaced. The microAeth MA200 uses a roll of Polytetrafluoroethylene (PTFE) filter material housed in a filter tape cartridge which has 15 sampling locations that can automatically advance. The microAeth MA300 and MA350 use a roll of Polytetrafluoroethylene (PTFE) filter material that is housed in a filter tape cartridge which has 85 sampling locations that can automatically advance. Filter tape cartridges have to be manually replaced much less often than a single use filter strip.

Can I make measurements using the AE51 while it is plugged in?

The AE51 is designed to operate off of its internal battery. It can be supplied from an external power source to extend operation to multiple days (or as long as the filter does not saturate and require replacement). In this case, additional external electrical noise from the external USB port or wall charger may be present in the data. This usually smooths out via post-processing techniques, but a more frequent timebase should be used to avoid group delay in the data when post-processed.

How long is the AE51 battery's run time per full charge?

The instrument’s run time is largely based on the settings used. Please refer to the run time chart in the AE51 Quick Start Guide. As an operational baseline, all AE51 instruments are tested to run for at least 24 hours at 100 ml/min and a 300 second timebase.

How long does it take to charge the AE51's battery?

Approximately 4-5 hours from 0% to 100% charge with the instrument turned off.

When do I need to have the AE51 battery replaced?

The AE51 uses an internal 1950 mAh rechargeable lithium-ion battery. After ~500 charge cycles, these batteries and others of lithium-ion chemistry will typically decrease to 80% capacity. This is also very dependent on many other factors such as discharge rate and temperature during use. After many charge cycles, the AE51’s battery capacity will gradually decrease until the end of its useful life. AethLabs can provide battery replacement service. Click here to request a quote.

When do I need to have the AE51 pump replaced?

While the AE51 pump manufacturer specifies a general pump lifetime of approximately 3,000 hours of operation, the pump’s longevity as an internal component of the AE51 is dependent on many factors which make it difficult to predict the exact timeline for pump replacement. For example, wear due to flow rate, exposure to high concentrations of particulate matter, varying atmospheric conditions, proper instrument usage and maintenance, and product variability all can impact the pump’s longevity. Common signs of pump wear are a lower maximum flow rate and increased flow instability. As AethLabs has continued to optimize the design and software of the AE51, the pump used in the instrument has been replaced by a new version with better performance characteristics and operational lifetime. If you have questions about your pump performance, or you are using an older model AE51 and want to ensure good data quality going forward, AethLabs offers a pump replacement service. Click here to request a quote.

When do I need to have the microAeth internal flowmeter(s) replaced?

Typically, the internal flowmeter(s) only needs to be replaced when water is ingested into the instrument. Nonetheless, a flowmeter’s longevity as an internal component of a microAeth is very dependent on many factors of use such as flow rate, exposure to high concentrations of particulate material, variant atmospheric conditions, proper instrument usage and maintenance, and manufacturing variability which make it difficult to predict the exact timeline for a flowmeter’s replacement. The AE51 has 1 internal flowmeter while the MA200, MA300, and MA350 all have 2 internal flowmeters to enable the use of the DualSpot® loading compensation method.

Can I use the DualSpot loading compensation method in the microAeth AE51?

No. The DualSpot® loading compensation method requires specialized internal hardware and firmware that are not built into or compatible with the microAeth AE51.

When I plug in a cable to the AE51, sometimes the amber charge LED is on and sometimes it only flashes on. What does this mean?

If the amber LED turns on and stays on, this indicates that the battery is charging.

The amber LED may blink on and then turn off quickly when attached to power. This may indicate that the instrument is charged. Due to charge indicator hysteresis, we recommend charging for an additional hour to ensure a full battery charge.

For best charging operation, we recommend charging the instrument for 5 continuous hours with the instrument turned off.

What is the internal data storage capacity of the AE51?

The internal memory capacity is 4 MB, and can store up to 127,999 lines of data. Every time you start and stop a measurement on the device, a small additional amount of memory is used as a header for the next data session. Storage capacity will depend on how many individual data sessions are generated. As an absolute maximum, if all memory was theoretically consumed by a continuous data file, the total elapsed time before the memory is full is approximately:

  • 1s timebase: 2,133 minutes or 35.5 hours
  • 10s timebase: 21,333 minutes or 355 hours or 14.8 days
  • 30s timebase: 63,999 minutes or 1,066 hours or 44.4 days
  • 60s timebase: 127,999 minutes or 2,133 hours or 88.8 days
  • 300s timebase: 10,666 hours or 444 days

Using microAeth MA200, MA300, & MA350

Do I need to change the filter strip in the microAeth MA200, MA300, and MA350?

No. The MA200, MA300, and MA350 do not use filter strips. Instead, there is a roll of filter material in a miniature cartridge that is used in the MA200, MA300, and MA350 that needs to be replaced much less frequently. This filter tape cartridge is similar to an audio cassette.

The MA200 filter tape cartridge contains enough material for 15 automatic sampling location advances.

The MA300 and MA350 filter tape cartridge contains enough material for 85 automatic sampling location advances.

How often do I need to change the filter tape cartridge in the microAeth MA200, MA300, and MA350?

Filter tape cartridge life depends on the BC concentrations you are measuring, the duration of the sampling events, the analytical measurement wavelength(s) enabled, and the flow rate and automatic tape advance settings of the instrument. These variables contribute proportionally to the rate of loading of particulate matter on each location of the filter tape and how often an automatic tape advance will occur. Once the filter is saturated, the data being collected are no longer useful, so in SingleSpot mode it is important keep the filter tape loading to a lower value and to set an automatic tape advance trigger value suitable for the average concentrations in the sampling environment. Managing and predicting filter tape cartridge changes in the MA200, MA300, and MA350 is much easier since these instruments can automatically advance to a new filter sampling location and contain 15 (MA200) or 85 (MA300 and MA350) times the sampling locations of the AE51 filter strip.

It will be necessary to change filter tape cartridges according to the sampling conditions and the instrument settings used. As an example, if the the 1-second timebase is selected, and assuming instrumental noise on the order of +/- 4µg/m3, if the average concentration of BC is ~1µg/m3 then the instrumental noise will cause fluctuations between positive and negative values with excursions of ~ +5µg/m3 and -3µg/m3 respectively. Within the noise the signal does exist but the data must be smoothed for a longer period of time in order to resolve it. These positive and negative excursions due to instrumental noise will average out to the BC value. Additionally if measuring high concentrations of say 50µg/m3 with the same settings, the instrumental noise will remain unchanged, yet the signal (50µg/m3) to noise (+/-4 µg/m3) ratio is much improved and the variation in the data due to noise is less noticeable, and in this case always positive (50µg/m3 +/-4µg/m3). microAeth users can always upload their data file to our server and use our post-processing tools to smooth their data. There are a few different algorithms available for data smoothing. Register for a Dashboard account here

How much filter tape material is in the microAeth MA200, MA300, and MA350?

The MA200, MA300, and MA350 use new miniature filter tape cartridges that contain a roll of filter material. Because there is a long roll of material contained in these cartridges that is automatically advanced, the filter tape cartridge needs to be replaced much less frequently than an AE51. This filter tape cartridge is similar to an audio cassette.

The MA200 filter tape cartridge contains enough material for 15 automatic sampling location advances.

The MA300 and MA350 filter tape cartridge contains enough material for 85 automatic sampling location advances.

Do I need to turn the MA200, MA300, and MA350 off before changing the filter?

No. The MA200, MA300, and MA350 automatically know when a filter tape cartridge has reached the end of the filter roll and will no longer sample and make measurements. The MA200, MA300, and MA350 also automatically know when a filter tape cartridge is not installed and will not allow sampling and measurements to begin. The on-board user interface needs to be used to replace the filter tape cartridge. The instructions for replacing the filter tape cartridge are on page 24 of the MA Series Operating Manual.

Do I need to save the MA200, MA300, and MA350 filter tape cartridges after sampling?

No. Because the MA200, MA300, and MA350 analyze and internally record data in real-time, you do not need to save the filter tape cartridge for further analysis.

Do all the microAeth use the same filters?

No. The microAeth AE51 uses a T60 Teflon-coated borosilicate glass fiber filter strip which has 1 sampling location and must be manually replaced. The microAeth MA200 uses a roll of Polytetrafluoroethylene (PTFE) filter material housed in a filter tape cartridge which has 15 sampling locations that can automatically advance. The microAeth MA300 and MA350 use a roll of Polytetrafluoroethylene (PTFE) filter material that is housed in a filter tape cartridge which has 85 sampling locations that can automatically advance. Filter tape cartridges have to be manually replaced much less often than a single use filter strip.

Can I make measurements using the MA200, MA300, and MA350 while they are plugged in?

Yes. The MA200, MA300, and MA350 can make measurements while plugged into external power through the DC barrel jack. It is highly recommended to use the DC barrel jack instead of the USB port to supply power to the instrument while measuring as power via USB may introduce additional noise to measurement data. It is also important to be aware of the quality of your external power source whenever making measurements while connected to a power source as noisy power supplies may introduce additional noise to measurement data.

How long does it take to charge the batteries in the MA200, MA300, and MA350?

All estimates are assuming the instrument turned off.
MA200:
Fast charging DC via barrel jack AC adapter: ~3 hours
USB charging: ~6.5 hours
MA300:
Fast charging DC via barrel jack AC adapter: ~11.75 hours
USB charging: ~25.75 hours
MA350:
Sealed connector for fast charging DC via barrel jack AC adapter: ~11.75 hours
USB charging on inside panel: ~25.75 hours

It is highly recommended to use the DC barrel jack for charging and power. Power via USB may introduce additional noise to measurement data.

When do I need to replace the battery in the MA200, MA300, and MA350?

The MA200 uses an internal 3200 mAh rechargeable lithium-ion battery while the MA300 and MA350 use an internal 12800 mAh rechargeable lithium-ion battery. After ~500 charge cycles, these batteries and others of lithium-ion chemistry will typically decrease to 80% capacity. This is also very dependent on many other factors such as discharge rate and temperature during use. After many charge cycles, the MA200’s battery capacity will gradually decrease until the end of its useful life. AethLabs can provide battery replacement service. Click here to request a quote.

When do I need to have the microAeth internal flowmeter(s) replaced?

Typically, the internal flowmeter(s) only needs to be replaced when water is ingested into the instrument. Nonetheless, a flowmeter’s longevity as an internal component of a microAeth is very dependent on many factors of use such as flow rate, exposure to high concentrations of particulate material, variant atmospheric conditions, proper instrument usage and maintenance, and manufacturing variability which make it difficult to predict the exact timeline for a flowmeter’s replacement. The AE51 has 1 internal flowmeter while the MA200, MA300, and MA350 all have 2 internal flowmeters to enable the use of the DualSpot® loading compensation method.

Can I use the DualSpot loading compensation method in the MA200, MA300, and MA350?

Yes. The DualSpot® loading compensation method is built into the microAeth MA200, MA300, and MA350. The use of the DualSpot® loading compensation method in the microAeth MA200, MA300, and MA350 is an optional user selectable feature.

Flow Calibration

Do microAeths need to have their flow system calibrated?

Yes. With ongoing use of your microAeth AE51, MA200, MA300, and MA350, the programmed internal flow rates may require flow recalibration to maintain accurate measurements. We suggest that the flow rates at the inlet of the AE51, MA200, MA300, and MA350 are checked and not necessarily recalibrated using a recently calibrated low backpressure external flowmeter before instrument deployment.

How often do I need to calibrate the flow of the microAeth AE51?

We suggest that the internal flow rates of the AE51 as shown streaming in the microAethCOM application, or saved in data files, are compared to the reported flow rates of a recently calibrated low backpressure external mass flowmeter before instrument deployment. If using the 50ml/min flow setpoint and the flow reported in microAethCOM is on average within 5% of the flow reported by the external flowmeter, we would not suggest altering the flow calibration table. For other higher flow setpoints (100ml/min and greater), if the instrument reported flow rate in microAethCOM or in the data file are off by more than 2-3% it may be a good time to recalibrate those setpoints. It is possible to calibrate to within 1-2% on average using the AethLabs Automatic AE51 Flow Calibration Kit.

How often do I need to calibrate the flow of the microAeth MA200, MA300, and MA350?

We suggest that the flow rates at the inlet of the MA200, MA300, and MA350 are checked and not necessarily recalibrated using a recently calibrated low backpressure external mass flowmeter before instrument deployment. It is possible to calibrate to within 1-2% on average using the AethLabs MA Series Flow Calibration Kit. Only the external mass flowmeter provided in the AethLabs MA Series Flow Calibration Kit is compatible with the MA200, MA300, and MA350.

How does the microAeth flow calibration work?

The flowmeter(s) and pump in the microAeth are calibrated to an accurate flow rate for each setpoint using a recently calibrated low backpressure external mass flowmeter as a reference standard. Many commercial flowmeters are mass flowmeters. They calculate a flow rate by measuring the amount of gas molecules (or mass of the gas) moving through the device during a certain amount of time. However, because we commonly measure gases such as air as the volumes they occupy (as cc's or liters, for instance), usually at standard atmospheric pressure and temperature, flowmeters most often report flow rates not as a mass unit over time, but as a volume unit over time using additional temperature and pressure sensors. The microAeth internal flowmeter(s) also measure mass flow and convert these values to volumetric values using a flow calibration table. All microAeth instruments are flow calibrated here in San Francisco at the time of production, at approximately standard atmospheric pressure and room temperature to ensure accurate flow rates.

Can I perform a manual flow calibration on the AE51 myself?

Yes. Manual flow calibration software is provided on the CD included with your AE51, and the latest version is available for download on the AethLabs website. Please follow all instructions for manual flow calibration in the AE51 Operating Manual. The manual flow calibration software allows you to use an external flowmeter to calibrate the included setpoints of the AE51. Not all external flowmeters are compatible with the AE51’s flow system design, as their measurement principle may have higher levels of backpressure that make it difficult to flow calibrate the high (~200ml/min or higher) or low (~50ml/min or lower) flow rates used by the AE51. In order to ensure that your AE51’s internal flow rate setpoints are accurate, the AethLabs AE51 Flow Calibration Kit is recommended for both automatic and manual flow calibration of the AE51. The AethLabs AE51 Flow Calibration Kit features a thermal MEMS-type external flowmeter, and all tubing, filters, fittings and cables needed as well as the latest version of the microAeth AE51 automatic flow calibration kit software. The kit automates the calibration process under computer control. Click here to request a quote.

AethLabs also offers flow calibration service and standard maintenance service (including full diagnostics, cleaning, flow calibration, and instrument testing) at the AethLabs San Francisco office.

Can I perform an automatic flow calibration on the AE51 myself?

Yes. The automatic flow calibration of the microAeth AE51 is performed using the AethLabs AE51 Flow Calibration Kit. The AethLabs AE51 Fllow Calibration Kit is recommended for both automatic and manual flow calibration of the AE51. The AethLabs AE51 Flow Calibration Kit features a thermal MEMS-type external flowmeter, and all tubing, filters, fittings and cables needed as well as the latest version of the microAeth® AE51 automatic flow calibration kit software. The kit automates the calibration process under computer control. Click here to request a quote.

AethLabs also offers flow calibration service and standard maintenance service (including full diagnostics, cleaning, flow calibration, and instrument testing) at the AethLabs San Francisco office.

Can I perform an automatic flow calibration on the MA200, MA300, and MA350?

Yes. The automatic flow calibration of the microAeth MA200, MA300, and MA350 is the only possible process to use to flow calibrate the instruments. The only way to perform a flow calibration on the MA200, MA300, and MA350 is to use a microAeth MA Series Flow Calibration Kit provided by AethLabs. Because of the specialized requirements of calibrating the MA200, MA300, and MA350, a custom designed external mass flowmeter that is a part of the microAeth MA Series Flow Calibration Kit must be used for automatic flow calibration. The automatic flow calibration process is very simple and does not require the removal or replacement of the installed filter tape cartridge as long as there is 1 unused sampling location still remaining. No external computer or software is needed to run the automatic flow calibration of the MA200, MA300, and MA350.

AethLabs also offers flow calibration service and standard maintenance service (including full diagnostics, cleaning, flow calibration, and instrument testing) at the AethLabs San Francisco office.

Can I perform a manual flow calibration on the MA200, MA300, and MA350?

No. A manual flow calibration of the microAeth MA200, MA300, and MA350 is not possible as the flow system is complicated and requires the flow calibration of two internal flowmeters. The only way to perform a flow calibration on the MA200, MA300, and MA350 is to use a microAeth MA Series Flow Calibration Kit provided by AethLabs. Because of the specialized requirements of calibrating the MA200, MA300, and MA350, a custom designed external mass flowmeter that is a part of the microAeth MA Series Flow Calibration Kit must be used for automatic flow calibration. The automatic flow calibration process is very simple and does not require the removal or replacement of the installed filter tape cartridge as long as there is 1 unused sampling location still remaining.

AethLabs offers flow calibration service and standard maintenance service (including full diagnostics, cleaning, flow calibration, and instrument testing) at the AethLabs San Francisco office.

Do I need a computer to flow calibrate the MA200, MA300, and MA350?

No. All that is needed is your microAeth MA200, MA300, or MA350, your microAeth MA Series Flow Calibration Kit and external power sources.

Can elevation affect the flow calibration of the microAeth?

Yes. Air density and pressure decrease as elevation increases from sea level. At higher elevations than the sea-level elevation at which microAeth are initially flow calibrated, you may see an offset in the rate in instrument flow. If you are at a much higher elevation, the decrease in air density most likely will require the pump running at a higher speed to pull through it a larger volume of air at a lower pressure that has the same mass of air as a smaller volume of air at a lower elevation and higher pressure. If you have large changes in elevation or significant environmental differences, this may affect the flow calibration of your instruments. While the instrument will control the flow system and mass flow will remain constant, the volumetric flow rate may change due to the changing density. Hence, the inlet of the microAeth should be checked for accurate flow rates after any large change in elevation.

In general, and especially for sampling at higher elevations, AethLabs suggests calibrating the flow of your microAeth in the location at which you plan to use it. This will ensure that the internal mass flowmeter is calibrated for the in situ atmospheric pressure. Please contact AethLabs technical support for more information about high altitude operation of the instrument.

Software / Connectivity

How do I install / upgrade the AE51 microAethCOM software and firmware?

All new microAeth AE51 come with a CD of the most recent version of the microAethCOM software package at the time of sale, which includes firmware and the manual flow calibration software versions. Page 5 of the AE51 Quick Start Guide or page 14 of the AE51 Operating Manual has instructions for PC software installation. Page 23 of the AE51 Operating Manual has instructions for upgrading the AE51 operating system firmware. The software and firmware can also be downloaded from the AethLabs website. Sign up for a free dashboard account here

Can I load the microAethCOM software onto multiple computers?

Yes. The AE51 microAethCOM and AE51 flow calibration software may be loaded onto multiple computers.

Why won't my computer recognize the AE51?

Is the instrument powered on? Is the USB cable provided with the instrument being used? Only 1 microAeth AE51 can be connected to your computer at a time. Make sure only 1 type of AE51 software is open at once. Contact AethLabs Support for further help if required. When you contact us, please let us know the serial number of your microAeth AE51, instrument firmware version, the version of your microAethCOM software, and computer operating system.

Accessories

Is the included sample tubing important?

Yes. The included sample tubing is made of non-contaminating and non-outgassing polyurethane that is designed to dissipate electrostatic discharge from air passing through the tube. This prevents particles from collecting on the tubing wall by limiting localized concentrations of electrostatic charge.

How do I use the included sample tubing and lapel clip?

The included sample tubing is approximately one meter long and has a swivel threaded fitting designed to be attached to the inlet of the microAeth, allowing you to better direct the source of your desired sample of air into the instrument. For the purposes of personal exposure monitoring, the included lapel clip has a plastic loop that fits this sample tubing. The sample tube can be positioned in the breathing zone and can be clipped to clothing while comfortably keeping the microAeth in a pocket or other carrying device.

Do I need a size-selective inlet for my microAeth?

Typically, Black Carbon particles are smaller than one micron in diameter. The BC measurements of the microAeth will be unaffected by a size-selective inlet that limits particle size to less than 2.5 microns in diameter. However, in some sampling conditions with high concentrations of particulate material dominated by light scattering aerosols, such as dust or smoke from biomass fuels, there can be a prevalent fraction of larger-diameter particles. Contamination of the instrument optics can affect the ongoing performance of your microAeth, so it is helpful to prevent them from entering the instrument. Furthermore, some research groups like to ensure the same size fraction across all measuring devices. For these applications, and to add contamination protection for your microAeth in high concentrations, AethLabs offers a microCyclone™ filtration attachment that will limit the size of the particles entering the microAeth to less than 2.5 microns in diameter when used at a flow rate of 50ml/min. The microCyclone will also limit the size of the particles to less than 1.6 microns in diameter when used at a flow rate of 100ml/min. Read more about the microCyclone in the microCyclone Operating Manual. The microCyclone may not be appropriate for use with the microAeth MA200, MA300, or MA350 when using specific operating settings depending on flow rates and if DualSpot® loading compensation is enabled.

Do I need to clean my microCyclone?

Yes. The microCyclone’s dustcup collects particulate material with diameters larger than the cyclone’s size cutpoint. The frequency of cleaning depends on the flow rate, atmospheric concentration of particulate material, and total run time of your sampling. For more information on using, cleaning, and maintaining the microCyclone, please refer to the microCyclone Operating Manual.

Website / Dashboard

What can I do on the AethLabs Dashboard?

The AethLabs.com website offers microAeth users a platform of tools for managing and visualizing the data from their microAeth instruments. You can upload data to your account to create an online data repository, view your BC data along with basic analytics (such as standard deviations, attenuation, etc.), utilize post-processing tools (such as status/error flagging, smoothing algorithms, etc.), chart data files (for one or multiple instruments at a time), and share data files with AethLabs for troubleshooting purposes. You can begin accessing these features by registering for an AethLabs Dashboard account.

How large of a data file can I upload to chart on the Dashboard?

While the file size limit for data files uploaded to the Dashboard has a maximum file size of 100MB, the more likely limitation you'll see when dealing with large files is that parsing a large file (> 10MB) uses a lot of memory - especially for microAeth MA series instrument data files that have many more data columns and where we're doing a significant number of calculations in order to generate the analytics across the entire file, pull out data to show GPS points for mapping, etc. In the case that you hit this limit, you'll see an error that starts with something like the following: "File processing takes more memory than is available". At any given time, memory on the server may be consumed by several different processes happening at once, so there may be situations where a file of X size processes fine, but then a smaller file fails and shows the error above. You can certainly try to process the file again and see if that helps, otherwise the best course of action is to enable the "Split sessions into calendar days on export" in the Manage Data screen of the microAeth Manager before exporting the data file in CSV format. Assuming the data session spans multiple calendar days, choosing this option creates multiple smaller files (as opposed to one file for the entire session). Processing each of these files should complete. The dashboard is provided to customers as a courtesy for basic QA/QC and instrumentation support for smaller data sets. The dashboard is not currently meant as a complete data management and analysis solution. We hope to improve the capabilities of the data processing on the dashboard in future updates.

Data Analysis

Why do I have large peaks/troughs at the beginning or end of my data files?

It is a good idea to let the instrument warm up for the first 30 minutes as it can take some time for the filter and instrument to come to equilibrium. It is not uncommon to have an excursion in the data at the end of operation as the instrument is often plugged into an external supply or is being handled differently. AethLabs' data dashboard web server has an option to remove those data points at the beginning or end of the file. It can also be used to post-process data to help remove or post-process noisier data files with negative values.

What is the AE51's limit of detection?

As with all analytical instruments, there is some amount of noise in the AE51’s measurements. Even when zero values are observed, the actual measurements are +/- a deviation associated with the inherent variability of the instrument’s measurement principle. Therefore, the AE51 recognizes a variable signal even for a blank sample (an air sample that contains near-zero quantities or no Black Carbon). Statistically, the AE51’s limit of detection is defined as the concentration of Black Carbon that produces a signal three times the standard deviation of this inherent noise level. The limit of detection depends on both the flow rate and time base settings used, as well as the overall health of the instrument. As a baseline, using the highest performance settings of 200ml/min flow rate and a 300-second timebase, the limit of detection has been measured in a stationary clean air enclosed testing chamber to be 5 ng/m3.

What about relative humidity (RH) noise?

As with many other types of particle measurement instrumentation, changes in relative humidity can change the size and optical properties of particles. The AE51 may respond to rapid changes in relative humidity, such as leaving an air conditioned room or exiting a climate controlled building and encountering ambient outdoor air that has a higher or lower relative humidity, causing a momentary excursion in the data. The instrument will usually correct itself after a few measurements depending on the flow rate and change in RH. For locations with high RH variability, an external sample dryer or heater may be used to condition the sample.

Why do I have negative BC values in my data files?

Negative readings are not necessarily a concern. All measurements have noise, and in the case of the Aethalometer® method and thus with the microAeth®, some data points will be greater than the actual value, some will be lower than the actual value, these measurements average out to approximate the measured value. The magnitude of these deviations is dependent on the settings and usage of the instrument. Often times negative values contain valid information that is needed to post-process or smooth the data to a longer interval, so arbitrary removal of negative values may be detrimental to a dataset. Instrumental noise and sensitivity to external influences are proportional to the timebase and flow rate. The lower the flow rate, and/or the timebase, the lower the signal to noise ratio (fewer particles are collected in the same period of time) and thus the instrumental noise and sensitivity to rapid environmental changes may be greater.

What causes noisy data?

There are a few different reasons for noise in your data. Here are some things to consider:

Instrument Maintenance

When was the last time your instrument was serviced? Your microAeth may need cleaning. Standard maintenance is recommended annually (depending on frequency and conditions of use), and is especially important when the instrument has been operating in challenging situations, e.g. high concentrations or dusty environments.

Your pump may need to be upgraded or replaced. Older AE51 instruments used a pump that is less stable than the unit used currently in AethLabs' production. This AE51 pump can be replaced, in some situations providing 2-3 times the flow stability of the old unit, 50% less power consumption, reduced noise and ensuring that the 200ml/min flow setpoint can be attained. Instruments with old pumps should be sent back to AethLabs for upgrade service.

Does your AE51 have an AethLabs sticker on its case? If not, it may not have been manufactured or ever serviced/supported by AethLabs and we may be able to upgrade your AE51 for better performance! We would like to help or to at least know more about your research application and how we can better support you. For more information about support and possible upgrade services, or to open a case, please contact AethLabs support. When you contact us, please let us know the serial number of your microAeth AE51, instrument firmware version, the version of your microAethCOM software, and computer operating system.

Measurement Sensitivity

It is important to select the appropriate instrument settings for your sampling campaign. Page 3 of the AE51 Quick Start Guide lists recommended settings for different scenarios. Instrument sensitivity is proportional to timebase and flow rate, the higher the flow rate and longer the integration time, the better the sensitivity, and the smaller the chances of influence by environmental factors or mechanical shock. Noise in your data may be caused by vibration or impact to the instrument, and this noise would be amplified if the instrument is operating at the shortest timebase setting.

Operation

microAeth AE51: The filter strip in the microAeth AE51 may not have been changed before the filter strip saturated resulting in periods of data collection that are likely invalid. The filter strip may have been replaced without first shutting the instrument down causing the optical signals to not be calibrated for the new filter and potentially causing measurement errors.

microAeth MA200, MA300, and MA350: The automatic filter tape advance value may have been set too high for the current sampling campaign environment. As a result, the current sampling location of the filter tape cartridge may have had too high ATN values or become too saturated resulting in periods of problematic collection and measurement. Better data results may possibly occurred if the automatic filter tape advance value had been set to a value that would have resulted in lower ATN values.

The instrument settings may not have been appropriately selected for the measurement environment; there is a trade-off between instrument sensitivity and the measurement interval and flow rate settings of the instrument, please refer to the AE51 Operating Manual and MA Series Operating Manual or AE51 Quick Start Guide for more information.

The instrument may be connected to a noisy external power supply causing an increase in instrumental noise that is most often seen when trying to measure low BC concentrations.

Which smoothing algorithm should I use?

Once you have signed up for a free account on AethLabs' dashboard, you will be able to access various smoothing algorithms and apply them to your data. Choosing the best algorithm to use depends on your data and analysis needs. Following is a brief explanation of each:

  • ONA is a variable window smoothing algorithm that uses the change in attenuation (ATN) to determine the smoothing window size. AethLabs' implementation of the ONA Algorithm is based on (this publication) by Hagler et. al., but the implementation may vary slightly.
  • Centered Moving Average calculates the mean of the data using an averaging window of n data points. There is no shift or group delay in the data using the centered moving average, unlike a simple moving average.
  • Local Polynomial Regression is a smoothing technique that helps correlate the other data points locally near to each data point. This local polynomial regression utilizes the Savitzky-Golay Filter.

Does the timestamp recorded in each data line refer to data collected in the preceding time interval or the following time interval?

The Black Carbon (BC) value is derived using a change in attenuation (ATN) from a starting measurement and an additional measurement at the end of the timebase period. The gradual accumulation of optically-absorbing particles leads to an increase in ATN from one period to the next. The BC value is therefore calculated and reported at the end of the measurement interval.

Customer Support

We’re available to help answer questions, and service your instrument should it become necessary. In order to establish a case related to your issue or concern, we ask that you first fill out the support inquiry form. By using the inquiry form, the AethLabs team will receive immediate notification of your request and our case management system will help us to track your inquiry until it is resolved. Click here to to start a support inquiry