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Frequently Asked Questions

Frequently Asked Questions

ATMOS

  • ZL6 - ATMOS 41 - ATMOS Does the ATMOS 41 and ZL6 conform to the ASABE Automatic Agricultural Weather Stations Guidelines?
    From Table 1 of “Measurement and Reporting Practices for Automatic Agricultural Weather Stations“, the ATMOS 41 internal measurement sequence meets the sampling interval guidelines for the weather variables listed. The ZL6 data logger can be configured to report values each hour, as stated in Table 1; however, some min/max instantaneous values are not available when using the ZL6 for data acquisition and delivery. Consult the ATMOS 41 user manual for details on the output values processed in METER data loggers.
  • ATMOS 41 - ATMOS What do the ATMOS 41 output data look like in a downloaded excel file from a ZL6?

    See image below.

     

  • ATMOS 41 - ATMOS How frequently are measurements taken?
    The ZL6 makes a measurement from each of the sensor ports in use every 60 s. However, the minimum measurement interval is five minutes for uploading data to ZENTRA Cloud. One-minute measurement interval is possible if you disable uploading data to ZENTRA Cloud, and these instructions are available upon request.

     

    The ATMOS 41 measures the solar radiation and temperature once every 10 s and records the instantaneous values. When queried, the ATMOS 41 outputs the average of the instantaneous measurements since the last query.

     

    The ATMOS 41 measures the wind speed and direction once every 10 s and records the instantaneous wind vector components. When queried, the ATMOS 41 outputs the average of the instantaneous measurements since the last query for wind speed and direction and the maximum instantaneous wind speed value for wind gust.

     

    The anemometer samples every 10 s (or more often if requested for non-METER logger). The gust speed reported is the highest instantaneous wind speed measured during the selected averaging interval (must be >20 s or gusts will equal speed).

     

    If using a non-METER logger, then the ATMOS 41 can be scanned every three seconds, but it is not necessary to oversample the ATMOS 41 and compute averages, accumulations, and maximums in external data systems because the ATMOS 41 has an internal measurement sequence [see the integrator guide for more information]. Less frequent sampling has the additional benefit of decreasing data acquisition systems and ATMOS 41 power consumption.
  • ATMOS 22 - ATMOS 41 - ATMOS What is the highest resolution scan rate for the ATMOS 22 and ATMOS 41?
    • With the ATMOS 41 and the M command, using a non-METER data logger, you can make measurements every 3 seconds.
    • With the ATMOS 22 and the M command, using a non-METER data logger, you can make measurements every 1 second.
    • Consult the integrator guides for more information.
    • Contact METER if your application requires more frequent measurements.
  • ATMOS 41 - ATMOS How do I replace the ATMOS 41 RH/temperature/barometric pressure sensor daughter board?
    It is recommended to replace the ATMOS 41 daughter board every two years.
    1. Instructions
    2. Video
  • ATMOS 41 - ATMOS What is the footprint of the ATMOS 41 (i.e., what area does it cover)?
    The ATMOS 41 is a microclimate sensor, so you should position it to be representative of the climate relevant to the research questions you are asking. FAO56 gives guidelines to the positioning and field size of sensors, so if you intend to use the sensor for reference ET, follow those guidelines. The footprint of a micro-meteorological measurement depends on the height of the sensor(s), the wind speed, and the sensible heat flux and is not a simple calculation.
  • ATMOS 41 - ATMOS Is there a bird deterrent that METER recommends for the ATMOS weather station?
    METER offers a bird deterrent ring that slides snugly onto the ATMOS funnel.
    See an image and installation instructions here.
  • ATMOS 22 - ATMOS How frequently are measurements taken?
    The ZL6 makes a measurement from each of the sensor ports in use every 60 s. However, the minimum measurement interval is five minutes for uploading data to ZENTRA Cloud. One-minute measurement interval is possible if you disable uploading data to ZENTRA Cloud, and these instructions are available upon request. The ATMOS 22 measures the wind speed and direction once every 10 s and records the instantaneous wind vector components. When queried, the ATMOS 22 outputs the average of the instantaneous measurements since the last query for wind speed and direction and the maximum instantaneous wind speed value for wind gust.

     

    If using a non-METER logger, then the ATMOS 22 can be scanned every 1 second, but it is not necessary to oversample the ATMOS 22 and compute averages, accumulations, and maximums in external data systems because it has an internal measurement sequence [see the integrator guide for more information]. Less frequent sampling has the additional benefit of decreasing data acquisition systems and ATMOS 22 power consumption.
  • ATMOS 14 - ATMOS Is the ATMOS 14 sensor chip/board removable?
    No, the ATMOS 14 sensor chip/board is not removable. The Teflon and Screen could be replaced. Contact METER for information. Long-term drift is stated in the manual. The ATMOS 14 shouldn’t need to be checked for drift until two years of field use.  There are instructions in the manual about checking relative humidity drift. The cost to recalibrate ATMOS 14 sensors at METER is about $100-$120.
  • ATMOS 22 - ATMOS What do the ATMOS 22 output data look like in a downloaded excel file from a ZL6?

    See image below. NOTE: The ATMOS 22 temperature measurement should not be used as an accurate measurement of air temperature. Testing has shown errors of as much as 2 °C between the ATMOS 22 temperature sensor and the true air temperature under sunny conditions. The speed of sound is temperature dependent, so the ATMOS 22 temperature measurement is important for the wind speed and direction calculations, but the lower accuracy of air temperature measurements is not an issue for the wind calculations.

  • ATMOS 22 Can I install my ATMOS 22 at a 90 deg angle for vertical wind speed?
    The ATMOS 22 should measure in any orientation if its measurement path is parallel to the wind flow. However, it should not be mounted at 90 degrees outside. This is due to rain obstructing the measurement during rain storms and possibly that water could be retained where the sonic transducers are, which would affect the measurement. Vertical wind speed outside is also associated with upward and downward eddies. These have both a horizontal and vertical component to them. If you mount an ATMOS 22 sideways, you would block the horizontal movement of these eddies and, presumably, negate any reason for doing it in the first place. The ATMOS 22 would be appropriate for measuring vertical wind velocity in certain indoor situations where the sensor is protected from pooling water and the wind vector is vertical (e.g., velocity in vertical HVAC ductwork).
  • ATMOS 41 - ATMOS Does the ATMOS 41 need to be powered continuously?
    Yes. There isn’t a way to get meaningful data from the ATMOS 41 without powering it continuously and letting its internal measurement sequence operate. The ATMOS 41 could be powered up at a set interval, allowed to take the first set of measurements, and then those could be output.  But this scheme would miss nearly all precipitation, nearly all lightning, and would grab a single, instantaneous value of wind speed and direction, which is almost meaningless considering the inherent variability in wind.  One thing to note is that the ATMOS 41 has been designed specifically to use as little power as possible in normal continuous-power mode.  The average current consumption is on the order of 200 micro-amps.  Even if the non-METER data acquisition device runs on just a few AA cells, it should be able to sustain this power draw for a very long time.
  • ATMOS 22 - ATMOS 41 - ATMOS What is the practical lower limit of the wind speed measurement for the ATMOS 22 and ATMOS 41?

    The practical lower limit for wind speed is about 0.03 m/s for our sonic anemometer. This is much better than cup anemometers, for example, which struggle making measurements below 0.5 m/s at the minimum because of difficulty starting and stopping. Sonic anemometers can read five times lower than that, yet they don’t necessarily read absolute zero.

  • ATMOS 14 - SRS - IRT - ECT - PAR - PYR - ATMOS 22 - ATMOS 41 - PHYTOS 31 - ECRN-100 - ECRN-50 How do I assemble the anemometer mast?

    The anemometer mast is suitable to mount METER’s above-ground sensors: ATMOS 41, ATMOS 22, ATMOS 14, PAR, PYR, IRT, SRS, PHYTOS 31, ECRN-100, ECRN-50, and ECT. Additional brackets may be required for some products.

    Anemometer mast kit: 1 extendable mast (fiberglass), 1 guy ring, 1 guy rope (7.6 m nylon rope), 3 guy rope anchors, and 1 mast base with center peg and set screw.

    Mast diameter: 4.5 cm

    Mast adjustable length: 1.3 to 2.3 m

    Tools to bring to the field: measuring tape, long metal screwdriver, mallet, wrench, level, scissors, optional shovel, and lighter.

    Installation:  Position the mast base in the desired installation location, avoiding large rocks. Install the center peg using a mallet. Insert the mast into the base so that the center peg is inside the mast tube. With the mast in the base, turn the set screw so it is hand-tight against the mast. Then, gently turn the set screw with a wrench. Do not over tighten or the fiberglass pole will break. Put the guy ring over the extendable mast. Cut the guy rope into thirds (approximately 2.5 m each) and burn the ends with a lighter to prevent fraying. Position the rope anchors equidistant apart to be about 1 meter away from the mast. Screw the anchors into the soil at the same angle as the guy rope using a long metal screwdriver as a make-shift turning handle. Attach the guy rope to the guy ring in 3 equidistant holes (show below) using knots. Then knot each guy rope in the corresponding anchor. Pull the rope very tight and ensure the mast is level and straight.

    Once the mast is secure, move the adjustable lever up to release the extendable mast. Move the lever down to secure the mast to the correct height. Install instruments following the sensor quick start guides and manuals.

    Limitations: Rocky soils, long-term monitoring sites, locations with high animal traffic. The SRS extension arm may be too heavy for the fiberglass mast.

  • ATMOS 41 - ATMOS How does the ATMOS 41 anemometer compare to other sonic anemometers?

    See ATMOS 41 comparison testing and sensor-to-sensor variability data here.

  • ATMOS 41 - ATMOS How often should I send in my ATMOS 41 for recalibration?
    The pyranometer and RH/barometer daughter board should be replaced every two years. You can replace these parts yourself. Prices and instructions are available. Or, you can request an RMA from METER Support and ship the instrument to METER for updating the pyranometer and RH/barometer daughter board.
  • ATMOS 41 - ATMOS Do you have a heater option for the ATMOS 41 to measure liquid water from hail and snow?

    We do not have a heated version of the ATMOS 41 at this time.  The model to correct for temperature based on the energy balance should be good in all situations in which the radiation and wind sensors can collect reliable data, however, being buried in snow and ice may impede the function of both.  This sensor suite will certainly not be a universally great fit for all climates on earth.  If the winter precipitation is critical for your study other instruments will be necessary.

  • ATMOS 41 - ATMOS Grounding and lightning protection suggestions for ATMOS 41
    We expect that even at a two-meter height the ATMOS 41 is going to be a magnet for strikes.  A nearby lightning rod might cause some small underestimation of solar radiation, but if it were even a meter away, that effect would be minimal (for affecting pyranometer measurements).  So, a lightning rod would likely always be a good idea but certainly not convenient.  The taller installations are more important to protect. For sensors installed below the ground surface, use these guidelines.
  • ATMOS 41 - ATMOS What type of pole should I mount the ATMOS to?
    The ATMOS 41 and ATMOS 22 mounting type can be a meteorological stand, pole in cement, or tripod; 31.8 mm to 50.8 mm, 1.25” to 2.0” diameter. The ATMOS 41 is fitted with a V-bolt, allowing it to be mounted on top of most posts, poles, tripods, etc.

     

    Tighten the bolts by hand, and then use a wrench to gently finish tightening the bolts, securing the ATMOS flat and tight against the top of the stand with a flat top. Shims may be needed at the top to level the unit if the pole is not level. CAUTION: Do not over-tighten the V-bolt. This will cause the plastic ATMOS bracket to break.

     

    METER offers a low-cost anemometer mast that could be used to mount either the ATMOS 41 or ATMOS 22.
  • ATMOS 41 - ATMOS Installing the ATMOS 41 at high elevations
    The ATMOS 41 performs well at high elevation (tested at 3100 m), but during cold seasons, it may get buried in snow, and it will not count the frozen precipitation. Also, when frozen, the anemometer section will probably fill up with ice and not read correctly until the ice melts.

     

    METER doesn’t offer a heated rain gauge (or heated version of the ATMOS 41 sensor).  If you are thinking about an external heater for the ATMOS 41, one challenge you’ll face is powering an external heater. The power budget of the METER data logger doesn’t have room for a heater.
  • ATMOS 41 How does the ATMOS 41 record an accurate air temperature without a radiation shield?
    The ATMOS 41 collects all of the information necessary to correct for absorbed radiation in a biophysical model. Because the ATMOS 41 also measures wind speed and solar radiation, it is possible to use a simple energy balance calculation to correct the Tair measurement. After correction, error decreases to < 0.5 °C and yields better accuracy than commonly used passive ventilation radiation shields. The equation and experimental results are available in our application note.
  • ATMOS 41 - ZENTRA Cloud - ATMOS With a pyranometer, how quickly could you catch a problem such as a bird soiling the instrument with a service like ZENTRA?

    On a sunny day, within a few hours.  On a cloudy day, it might take a few days.

  • SC-1 Leaf Porometer - ATMOS Why doesn’t the Leaf Porometer output transpiration like the LI-COR used to?

    The SC-1 Leaf Porometer measures the vapor flux to arrive at stomatal conductance, which on the surface gives you leaf level transpiration. However, the leaf chamber of the SC-1 forces its own environment on the leaf, so the chamber steady-state transpiration will likely differ significantly from the environment steady-state transpiration. This is fine for stomatal conductance since the reading is taken within 30 seconds, but it doesn’t work for transpiration. We recommend you use independent atmospheric vapor pressure and leaf temperature measurements coupled with an estimate of leaf boundary layer conductance to calculate transpiration from the stomatal conductance measurement made with the SC-1.