ATMOS 41 Gen 2 All-in-One Weather Station
1. Introduction
Thank you for choosing the ATMOS 41 Gen 2 All-in-One Weather Station from METER Group. This station is designed for continuous monitoring of environmental variables, including standard weather measurements. The ATMOS 41 Gen 2 measures:
- Solar radiation
- Precipitation
- Precipitation electrical conductivity
- Air temperature
- Barometric pressure
- Vapor pressure
- Relative humidity
- Wind speed
- Wind direction
- Maximum wind gust
- Lightning strikes
- Lightning distance
- Tilt
All sensors are integrated into a single, compact unit, requiring minimal installation effort. Its robust design makes it ideal for long-term, remote installations. Applications include weather monitoring, microenvironment monitoring, spatially-distributed environmental monitoring, crop weather monitoring, fire danger monitoring, weather networks, and renewable energy assessment.
Additional advantages include its low-power design supporting battery-operated data loggers with SDI-12 or Modbus RS-485 interfaces. A tilt sensor warns of out-of-level conditions, and no configurations are necessary. Prior to use, verify all system components are included and in good condition.
2. Operation
Please read all instructions before operating the ATMOS 41 Gen 2 to ensure optimal performance.
PRECAUTION: METER sensors are built to high standards, but misuse, improper protection, or improper installation may damage the sensor and void the warranty. Follow recommended installation instructions and ensure proper protections are in place.
2.1 Installation
Follow the steps in Table 1 to set up the ATMOS 41 Gen 2 and begin data collection.
| Tools Needed | Details |
|---|---|
| Wrench (13 mm / 1/2 in) | Mounting pole 31.8 to 50.8 mm (1.25 to 2.0 in) diameter. Compatible US standard pipe sizes include 1.00-, 1.25-, and 1.50-in. Square tubing (1.25 to 2.00 in width) or T-posts also work. |
Field Site Considerations
Identify Mounting Location - Landscape: Choose a location considering vegetation cover, solar exposure, and wildlife activity. For WMO siting standards, ensure minimal slope and low vegetation height (< 10 cm) to prevent the pyranometer from being shaded.
Identify Mounting Location - Interferences: Select a site far from high electromagnetic interference (EMI) sources like power lines, metallic objects, heat sources, or bodies of water.
Conduct System Check: Plug the weather station into the logger (Section 2.2.1) and verify all sensors are functional and reading within expected ranges.
Install Mounting Pole: Use a pole with a 31.8 to 50.8 mm diameter. Mount the station approximately 2 m above ground, or adjust height based on application. The pole should be within 4.5° of level.
Mount Toward True North: Orient the 'N' engraving on the instrument to point true north (not magnetic north) for accurate wind direction measurements.
Mount and Secure Device: Tighten the V-bolt nuts hand-tight, then further with the wrench. Secure the ATMOS 41 Gen 2 flat and tight against the top of the mounting pole. CAUTION: Do not overtighten the bolt.
Level the Device: Use the bubble level on the ATMOS 41 Gen 2 to ensure it is level (within ±2°). Adjust by loosening the leveling screw, repositioning, and retightening.
Secure and Protect Cables: Install cables in conduit or plastic cladding to prevent damage. Gather and secure cables to the mounting mast.
Connect to Data Logger: Plug the sensor into a data logger and verify readings. Refer to Section 2.2 for more details.
2.2 Connecting
The ATMOS 41 Gen 2 works seamlessly with METER data loggers and is compatible with other loggers (e.g., Campbell Scientific, Inc.).
SDI-12 Communication: Requires 3.6 to 15.0 VDC excitation and operates at 2.8 to 5.5 VDC for data communication. Comes with a 3.5-mm stereo plug connector for METER loggers or can be ordered with stripped wires for third-party loggers.
Modbus RS-485: For Modbus RS-485 enabled units, excitation is 4 to 24 VDC, operating at 12 to -7 VDC for data communication.
Wiring Diagrams:
- Figure 1: 3.5-mm stereo plug connector wiring (Power: brown, Digital communication: orange, Ground: bare).
- Figure 2: Pigtail wiring (similar to Figure 1).
- Figure 3: Three-wire SDI-12 wiring diagram.
- Figure 4: Four-wire M12 connector SDI-12 wiring diagram.
- Figure 5: Four-wire M12 connector and pigtail adapter for screw terminals.
- Figure 6: Four-wire M12 connector RS-485 wiring diagram.
Connecting to METER Logger: Use ZENTRA Utility or ZENTRA Cloud for configuration. METER data loggers automatically recognize ATMOS 41 Gen 2 sensors. Set the measurement interval.
Note: The ATMOS 41 Gen 2 draws more current than other METER sensors; consider using only one ATMOS 41 Gen 2 per ZENTRA or EM60 data logger to manage battery life, especially in low-sunlight conditions.
Connecting to Non-METER Logger: Refer to the third-party logger manual and the ATMOS 41 Gen 2 Integrator Guide. Options include clipping the stereo plug or using an adapter cable.
2.3 Communication
The ATMOS 41 Gen 2 supports SDI-12 and Modbus RS-485 protocols.
2.3.1 SDI-12
SDI-12 requires unique sensor addresses. The default is '0'. Addresses can be changed using a ZSC Bluetooth sensor interface and the ZENTRA Utility Mobile app. The address must be returned to '0' for ZENTRA loggers.
2.3.2 Modbus RS-485
Uses Modbus RTU protocol over RS-485. The default address is '1'. Refer to the Integrator Guide for details on address changes and data registers.
3. System
This section describes the ATMOS 41 Gen 2 All-in-One Weather Station system.
3.1 Specifications
Measurement Specifications
| Measurement | Range | Resolution | Accuracy |
|---|---|---|---|
| Solar Radiation | 0-1750 W/m² | 1 W/m² | ±5% of measurement typical |
| Precipitation | 0-1,500 mm/h | 0.017 mm | ±5% of measurement from 0 to 1000 mm/hr |
| Vapor Pressure | 0-47 kPa | 0.01 kPa | Varies with temperature and humidity (see chart) |
(See Figure 7 for Vapor pressure sensor accuracy chart)
Relative Humidity
| 10% RH | 20% RH | 30% RH | 40% RH | 50% RH | 60% RH | 70% RH | 80% RH | 90% RH | 100% RH | |
|---|---|---|---|---|---|---|---|---|---|---|
| Temperature (°C) | ||||||||||
| 0 | ±0.01 | ±0.02 | ±0.03 | ±0.05 | ±0.09 | ±0.16 | ±0.27 | ±0.44 | ±0.69 | ±1.33 |
| 10 | ±0.01 | ±0.02 | ±0.04 | ±0.07 | ±0.12 | ±0.20 | ±0.32 | ±0.50 | ±0.99 | ±1.82 |
| 20 | ±0.01 | ±0.02 | ±0.04 | ±0.08 | ±0.14 | ±0.23 | ±0.36 | ±0.62 | ±1.26 | ±2.10 |
| 30 | ±0.01 | ±0.02 | ±0.04 | ±0.09 | ±0.15 | ±0.24 | ±0.39 | ±0.69 | ±1.40 | ±2.24 |
| 40 | ±0.01 | ±0.02 | ±0.05 | ±0.09 | ±0.16 | ±0.26 | ±0.42 | ±0.76 | ±1.54 | ±2.38 |
| 50 | ±0.01 | ±0.03 | ±0.05 | ±0.10 | ±0.17 | ±0.28 | ±0.45 | ±0.99 | ±1.68 | ±2.24 |
| 60 | ±0.02 | ±0.03 | ±0.06 | ±0.11 | ±0.18 | ±0.30 | ±0.47 | ±1.06 | ±1.82 | ±2.10 |
| 70 | ±0.02 | ±0.04 | ±0.07 | ±0.12 | ±0.20 | ±0.32 | ±0.50 | ±1.13 | ±1.96 | ±2.10 |
| 80 | ±0.03 | ±0.05 | ±0.09 | ±0.15 | ±0.26 | ±0.42 | ±0.66 | ±1.20 | ±2.24 | ±2.24 |
| 90 | ±0.03 | ±0.05 | ±0.09 | ±0.15 | ±0.26 | ±0.42 | ±0.66 | ±1.26 | ±2.24 | ±2.24 |
| 100 | ±0.03 | ±0.05 | ±0.09 | ±0.16 | ±0.27 | ±0.44 | ±0.69 | ±1.33 | ±2.38 | ±2.38 |
Air Temperature:
| Parameter | Value |
|---|---|
| Range | -50 to 60 °C |
| Resolution | 0.1 °C |
| Sensor Accuracy | ±0.2 °C |
| Measurement Uncertainty | ±0.6 °C (from -20 to 50 °C) |
(See Section 3.6.1 for Air Temperature Theory)
Humidity Sensor Temperature
| Parameter | Value |
|---|---|
| Range | -40 to 50 °C |
| Resolution | 0.1 °C |
| Accuracy | ±1.0 °C |
Barometric Pressure
| Parameter | Value |
|---|---|
| Range | 1-120 kPa |
| Resolution | 0.01 kPa |
| Accuracy | ±0.05 kPa at 25 °C |
| Equilibration | < 10 ms |
| Long-Term Drift | < 0.1 kPa/year, typical |
Horizontal Wind Speed
| Parameter | Value |
|---|---|
| Range | 0-60 m/s |
| Resolution | 0.01 m/s |
| Accuracy | The greater of 0.3 m/s or 6% of measurement |
Wind Gust
| Parameter | Value |
|---|---|
| Range | 0-60 m/s |
| Resolution | 0.01 m/s |
| Accuracy | The greater of 0.3 m/s or 6% of measurement |
Wind Direction
| Parameter | Value |
|---|---|
| Range | 0°-359° |
| Resolution | 1° |
| Accuracy | ±5° |
Tilt
| Parameter | Value |
|---|---|
| Range | 0° to 180° |
| Resolution | 0.1° |
| Accuracy | ±1° |
Lightning Strike
| Parameter | Value |
|---|---|
| Range | 0-65,535 strikes |
| Resolution | 1 strike |
| Accuracy | Variable with distance, >25% detection at <10 km typical |
Lightning Average Distance
| Parameter | Value |
|---|---|
| Range | 0-40 km |
| Resolution | 3 km |
| Accuracy | Variable |
(See Figure 18 for corrected air temperature comparison graph)
3.2 Solar Radiation (Pyranometer): Measures total incoming solar radiation using a silicon-cell sensor. A cosine-correcting head ensures accuracy regardless of sun angle. Calibration is performed by Apogee Instruments. Proper leveling and cleaning of the sensor surface are critical for accurate measurements. Note: Isopropyl alcohol and a microfiber cloth are recommended for cleaning.
(See Figure 9 for spectral response estimate)
3.3 Wind Speed and Direction (Anemometer): Measures wind speed and direction using ultrasonic signals that bounce off a convex base plate. The speed of sound is affected by wind, and calculations are based on the time differences of sound travel. The ATMOS 41 Gen 2 measures wind speed every 3 seconds, averaging the last 10 measurements. It also reports wind gust and direction. Note: Cup anemometers average over longer intervals, resulting in a lower peak-to-mean ratio for gusts compared to this ultrasonic anemometer.
(See Figure 10 for Anemometer diagram)
3.3.1 Wind Speed and Direction Theory: Explains the physics behind the anemometer's operation based on sound speed influenced by air temperature, vapor pressure, and atmospheric pressure. Equations are provided for calculating sound speed and wind vector components.
3.4 Vapor Pressure/Relative Humidity Sensor: Located behind the access door, protected by a Teflon screen. Measures relative humidity and temperature, and computes vapor pressure. Vapor pressure is a key indicator of atmospheric moisture. Note: The sensor should not be painted or coated.
(See Figure 11 for Vapor pressure sensor diagram)
3.5 Precipitation: Uses a 9.31-cm diameter rain funnel and two measurement methods: a drop counter (primary) and a tipping spoon (secondary). The drop counter uses gold electrodes to count drops of known size. The tipping spoon measures rainfall volume when it tips. Important: The ATMOS 41 Gen 2 must be within ±2° of dead level for accurate rainfall measurement.
(See Figure 12 for Rain funnel and rain gauge diagram)
3.5.1 Remove Rain Funnel: Instructions for removing the funnel for Bluetooth connection, cleaning, or pyranometer recalibration. Involves pressing down, twisting counter-clockwise, and lifting. CAUTION: Discharge static electricity before removal. Avoid damaging the pyranometer connector.
(See Figure 13 for removal diagram, Figure 14 for connector disconnect)
3.5.2 Electrical Conductivity (EC): Measures the EC of precipitation in a small basin using two electrodes. Affected by atmospheric depositions and biological substances. Regular cleaning of the funnel and basin is critical for accurate EC measurements.
3.6 Temperature Sensor: A thermistor housed in a stainless steel needle extends from the center of the anemometer. It measures air temperature and uses an energy balance correction (Equation 11) considering solar radiation and wind speed for accuracy. Note: The sensor should not be painted or coated.
(See Figure 17 for Temperature sensor diagram)
3.6.1 Air Temperature Theory: Details the energy balance correction formula (Equation 11) used to adjust measured temperature to actual air temperature.
3.7 Lightning Sensor: Detects lightning strikes and their distance by listening for AM signal disruptions. Outputs the total number of strikes and average distance. Accuracy for distance is variable, with >25% detection at <10 km.
3.8 Barometric Pressure Sensor: Measures atmospheric pressure, calibrated against secondary standards. It records instantaneous values and outputs averages when queried.
3.9 Tilt Sensor: Ensures the station remains level. Deviations from level can cause errors in solar radiation and rainfall measurements. It measures tilt every 60 seconds.
3.10 Limitations
The ATMOS 41 Gen 2 is robust but has limitations:
3.10.1 Snow and Ice Accumulation:
The station is not heated. Snow and ice accumulation in the funnel can lead to inaccurate precipitation measurements and affect solar radiation and wind measurements. Refer to maintenance notes for winter performance.
3.10.2 Heavy Rain and Strong Wind:
Water splashing off the base plate can interrupt ultrasonic signals. Hydrophobic membranes protect transducers, but heavy rain or wind can cause temporary water buildup, potentially interrupting measurements until conditions improve.
3.10.3 Electromagnetic Interference:
High EMI levels (e.g., from power lines) can adversely affect lightning and rainfall measurements. Locate the station away from EMI sources.
4. Service
This section covers calibration, recalibration, cleaning, maintenance, troubleshooting, customer support, and terms and conditions.
4.1 Calibration
- Solar Radiation: Calibrated via side-by-side comparison with reference pyranometers. METER recommends using the Clear Sky Calculator for uncertainty assessment.
- Precipitation: No individual calibration. Accuracy verified during manufacturing based on drop size and tipping spoon calibration.
- Air Temperature: Verified against NIST-traceable standards. Specified accuracy is 0.1 °C.
- RH/Vapor Pressure: Three-point calibration using a METER WP4C chilled-mirror dew point sensor. Calibrated against salt standards for accuracy.
4.2 Recalibration Recommendations
| Sensor Function | Measurement Drift | Calibration Frequency |
|---|---|---|
| Solar radiation | <2% drift/year | Every 2 yearsᵃ |
| Barometric pressure | 0.1 kPa/year (typical) | Every 1-2 yearsᵇ |
| Relative humidity | <0.25% RH/year | Every 2 yearsᵇ |
| All other sensors | - | Not needed |
ᵃ Calibrated, field-swapable replacement pyranometers are available from METER. Contact Customer Support.
ᵇ Barometric pressure and RH/vapor pressure sensors are housed on a field-swappable module. Contact Customer Support for replacement modules.
4.3 Cleaning and Maintenance
Refer to ATMOS cleaning instructions for detailed guidance.
CAUTIONS:
- DO NOT immerse the ATMOS 41 Gen 2 in water.
- DO NOT touch the temperature sensor needle (Figure 19) as its lead wires are delicate.
- Avoid applying more than light pressure on the ultrasonic transducers (Figure 19).
Cleaning Steps:
- Ensure the sensor is level after cleaning.
- Remove obstructions (cobwebs, leaves, etc.) from the temperature sensor and ultrasonic transducers (Figure 19).
- Check and clear debris from the rain funnel (Figure 22), pyranometer (Figure 22), ultrasonic transducer openings (Figure 19), and sintered glass reflection plate (Figure 10).
- Clean the ATMOS 41 body with a damp cloth and brush for crevices.
- Check the downspout (Figure 20) for debris.
- Inspect the Teflon screen (Figure 21) and replace if dirty. Contact Customer Support for a replacement screen.
4.4 Update Firmware
METER occasionally releases firmware updates. Consult Customer Support regarding the necessity or process of updating firmware.
4.5 Troubleshooting
| Problem | Possible Solutions |
|---|---|
| ATMOS 41 Gen 2 not responding | Check power supply, sensor cable integrity, and try a different logger port. For SDI-12, verify wiring (Brown: Power, Orange: Digital Out, Bare: Ground). |
| Water not flowing through rain gauge | Check spring, screen, and outflow for debris. Ensure the anemometer pathway is clear of obstructions. Check ultrasonic transducers for moisture and clean with a dry cloth. Ensure the convex base plate is clean. Ensure the unit is level. |
| No wind speed | Check ultrasonic transducers for water build-up; dab away moisture. Ensure the convex base plate (Figure 7) is clean. Ensure the unit is level. |
| No pyranometer reading | Ensure the pyranometer plug (Figure 23) is connected. Contact Customer Support if the pyranometer is damaged. |
| Not reading any rain or not measuring rain accurately | Remove debris from the rain gauge funnel. Ensure the ATMOS 41 Gen 2 is level (within ±2°). Gently twist and remove the funnel. Check that gold electrodes are aligned (Figure 24). Refer to calibration check procedures online. |
| No temperature reading | Check that the temperature needle is not pushed in, as this can break thermistor wires. Avoid applying excessive pressure when cleaning. |
4.6 Customer Support
North America: Available Monday-Friday, 7:00 am - 5:00 pm Pacific time. Contact via email (support.environment@metergroup.com, sales.environment@metergroup.com), phone (+1.509.332.5600), or fax (+1.509.332.5158). Website: metergroup.com.
Europe: Available Monday-Friday, 8:00 - 17:00 Central European time. Contact via email (support.europe@metergroup.com, sales.europe@metergroup.com), phone (+49 89 12 66 52 0), or fax (+49 89 12 66 52 20). Website: metergroup.com.
When contacting by email, include name, email address, phone number, instrument serial number, and a description of the problem. For products purchased through a distributor, contact the distributor directly.
4.7 Terms and Conditions
By using METER instruments and documentation, users agree to METER Group's Terms and Conditions. Refer to metergroup.com/terms-conditions for details.
Appendix A. Compliance Certifications
A.1 USA
This device complies with Part 15 of the FCC Rules. Operation is subject to conditions: no harmful interference and acceptance of received interference. The EM60 series loggers contain specific radio modules (FCC IDs listed). Modifications not approved by METER Group may void FCC compliance. Tested to comply with Class B digital device limits for residential installations.
Canada: Complies with Canadian CAN ICES-3(B) / NMB-3(B) and RSS-210. Operation subject to conditions: no interference and acceptance of interference. EM60 series loggers contain specific radio modules (IC IDs listed).
Radio Frequency (RF) Exposure Information: Details compliance with RF exposure limits for mobile exposure conditions.
A.2 European Union
Complies with R&TTED and bears the CE mark. Complies with radiation exposure limits for uncontrolled environments. Minimum distance of 20 cm between radiator and body required. Transmitter must not be co-located with other antennas/transmitters unless authorized.
A full CE declaration of conformity for the EM60 is available from METER Group upon request.
METER Group
