METER ATMOS 41 User Manual

ATMOS 41 INTEGRATOR GUIDE

SENSOR DESCRIPTION

The ATMOS41 All-in-One Weather Station is designed for continuous monitoring of environmental variables,
including all standard weather measurements (see Measurement Specifications). All sensors are integrated
into a single unit, requiring minimal installation effort. Ultra-low power consumption and a robust, no
moving parts design that prevents errors because of wear or fouling make the ATMOS41 ideal for long-term,
remote installations.

APPLICATIONS

• Weather monitoring

• Microenvironment monitoring

• Spatially distributed environmental monitoring

• Crop weather monitoring

• Fire danger monitoring/mapping

• Weather networks

18171-08

7.31.2020

ADVANTAGES

• Robust, no moving parts design

• Small form factor

• Integrated design for easy installation

• Low-input voltage requirements

• Low-power design supports battery-operated
dataloggers

• Supports the SDI-12 three-wire interface

• Tilt sensor informs user of out-of-level conditions

• No configuration necessary

• Measures all standard weather variables (plus
several others)

PURPOSE OF THIS GUIDE

METER Group provides the information in this
integrator's guide to help ATMOS41 All-in-One
Weather Station customers establish communication
between these sensors and their data acquisition
equipment or field data loggers. Customers using data
loggers that support SDI-12 sensor communications
should consult the data logger user manual. METER
sensors are fully integrated into the METER system of
plug-and-play sensors, cellular-enabled data loggers,
and data analysis software.

COMPATIBLE FIRMWARE VERSIONS

This guide is compatible with firmware versions

5.30 or newer.

METER Group, Inc. USA

2365 NE Hopkins Court, Pullman, WA 99163

T +1.509.332.2756 F +1.509.332.5158
E [e-mail] W metergroup.com

Figure 1 ATMOS 41 All-in-One Weather Station

SPECIFICATIONS

MEASUREMENT SPECIFICATIONS

Solar Radiation

Range 0–1750 W/m

Resolution 1 W/m

Accuracy

±5% of measurement typical

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2

Humidity Sensor Temperature

Range –40 to 50 °C

Resolution 0.1 °C

Accuracy ±1.0 °C

Precipitation

Range 0–400 mm/h

Resolution 0.017 mm

Accuracy ±5% of measurement

from 0 to 50 mm/h

Vapor Pressure

Range 0–47 kPa

Resolution 0.01 kPa

Accuracy Varies with temperature

and humidity, ±0.2 kPa
typical below 40 °C

Barometric Pressure

Range 50–110 kPa

Resolution 0.01 kPa

Accuracy ±0.1 kPa from –10 to 50 ºC

±0.5 kPa from –40 to 60 ºC

Horizontal Wind Speed

Range 0–30 m/s

Resolution 0.01 m/s

Accuracy The greater of 0.3 m/s or

3% of measurement

Wind Gust

Range 0–30 m/s

Resolution 0.01 m/s

Accuracy The greater of 0.3 m/s or

3% of measurement

Wind Direction

Range 0°–359°

Resolution 1°

Accuracy ±5°

Relative Humidity

Range 0–100% RH (0.00–1.00)

Resolution 0.1% RH

Accuracy Varies with temperature

and humidity, ±3% RH typical

Air Temperature

Range –50 to 60 °C

Resolution 0.1 °C

Accuracy ±0.6 °C

Tilt

Range –90° to 90°

Resolution 0.1°

Accuracy ±1°

Lightning Strike Count

Range 0–65,535 strikes

Resolution 1 strike

Accuracy Variable with distance,

>25% detection at <10 km typical

Lightning Average Distance

Range 0–40 km

Resolution 3 km

Accuracy Variable

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COMMUNICATION SPECIFICATIONS

Output

SDI-12 communication

PHYSICAL SPECIFICATIONS

Dimensions

Diameter 10 cm (3.94 in)

Height 34 cm (13.38 in), includes rain

gauge filter

Operating Temperature Range

Minimum –50 °C

Typical NA

Maximum 60 °C

NOTE: Barometric pressure and relative humidity sensors
operate accurately at a minimum of –40 °C.

ELECTRICAL AND TIMING CHARACTERISTICS

Supply Voltage (VCC to GND)

Minimum 3.6 VDC continuous

Typical NA

Maximum 15.0 VDC continuous

NOTE: ATMOS 41 must be continuously powered to workproperly.

NOTE: For the ATMOS 41 to meet digital logic levels specified
by SDI-12, it must be excited to 3.9 VDC or greater.

Digital Input Voltage (logic high)

Minimum 2.8 V

Typical 3.6 V

Maximum 5.0 V

Digital Input Voltage (logic low)

Minimum –0.3 V

Typical 0.0 V

Maximum 0.8 V

Digital Output Voltage (logic high)

Minimum NA

Typical 3.6 V

Maximum NA

NOTE: For the ATMOS 41 to meet digital logicl levels specified
by SDI-12, it must be excited to 3.9 VDC or greater.

Power Line Slew Rate

Minimum 1.0 V/ms

Typical NA

Maximum NA

Data Logger Compatibility

METER ZL6 and EM60 data loggers or any data
aquisition systems capable of switched 3.6- to

15.0-VDC excitation and SDI-12 communication

Cable Length

5 m (standard)
75 m (maximum custom cable length)

NOTE: Contact Customer Support if nonstandard cable length
is needed.

Connector Types

3.5-mm stereo plug connector or stripped and
tinned wires

Current Drain (during measurement)

Minimum 0.2 mA

Typical 8.0 mA

Maximum 33.0 mA

Current Drain (while asleep)

Minimum 0.2 mA

Typical 0.3 mA

Maximum 0.4 mA

Power Up Time (SDI ready)—aRx! Commands

Minimum NA

Typical 10 s

Maximum NA

Power Up Time (SDI ready)—Other Commands

Minimum NA

Typical 310 ms

Maximum NA

Power Up Time (SDI-12, DDI disabled)

Minimum NA

Typical 240 ms

Maximum NA

Measurement Duration

Minimum NA

Typical 110 ms

Maximum 3,000 ms

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Power (brown)

Ground

GND

GND

220PF

COMPLIANCE

Manufactured under ISO 9001:2015

EM ISO/IEC 17050:2010 (CE Mark)

EQUIVALENT CIRCUIT AND CONNECTION TYPES

Refer to Figure 2 and Figure 3 to connect the ATMOS 41 to a logger. Figure 2 provides a low-impedance variant
of the recommended SDI-12 specification.

PIGTAIL CABLE

DATA

Ground (bare)

Digital
communication (orange)

R1

510

R2

100K

Figure 2 Equivalent circuit diagram

C1

NOTE: Some early ATMOS41 units may have the older Decagon
wiring scheme where the power supply is white, the digital out is
red, and the bare wire is ground.

STEREO CABLE

Digital communication
Power

Figure 3 Connection types

PRECAUTIONS

METER sensors are built to the highest standards, but misuse, improper protection, or improper
installation may damage the sensor and possibly void the warranty. Before integrating sensors into a sensor
network, followthe recommended installation instructions and implement safeguards to protect the sensor
from damaging interference.

SURGE CONDITIONS

Sensors have built-in circuitry that protects them against common surge conditions. Installations in
lightning-prone areas, however, require special precautions, especially when sensors are connected to a
well-grounded third-party logger.

Visit metergroup.com for articles containing more information.

CABLES

Improperly protected cables can lead to severed cables or disconnected sensors. Cabling issues can be
caused by many factors, including rodent damage, driving over sensor cables, tripping over the cable, not
leaving enough cable slack during installation, or poor sensor wiring connections. To relieve strain on the
connections and prevent loose cabling from being inadvertently snagged, gather and secure the cable
travelling between the ATMOS 41 and the data acquisition device to the mounting mast in one or more places.
Install cables in conduit or plastic cladding when near the ground to avoid rodent damage. Tie excess cable to
the data logger mast to ensure cable weight does not cause sensor to unplug.

SENSOR COMMUNICATIONS

METER digital sensors feature a 3-wire interface following SDI-12 protocol for communicating
sensor measurements.

SDI12 INTRODUCTION

SDI-12 is a standards-based protocol for interfacing sensors to data loggers and data acquisition equipment.
Multiple sensors with unique addresses can share a common 3-wire bus (power, ground, and data). Two-way
communication between the sensor and logger is possible by sharing the data line for transmit and receive

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as defined by the standard. Sensor measurements are triggered by protocol command. The SDI-12 protocol
requires a unique alphanumeric sensor address for each sensor on the bus so that a data logger can send
commands to and receive readings from specific sensors.

Download the SDI-12 Specification v1.3 and learn more about the SDI-12 protocol.

DDI SERIAL INTRODUCTION

The DDI serial protocol is the method used by the METER family of data loggers for collecting data from
the sensor. This protocol uses the data line configured to transmit data from the sensor to the receiver only
(simplex). Typically, the receive side is a microprocessor UART or a general-purpose IO pin using a bitbang
method to receive data. Sensor measurements are triggered by applying power to the sensor. When the
ATMOS41 is set to address 0, a DDI serial string is sent on power up, identifying the sensor.

INTERFACING THE SENSOR TO A PC

The serial signals and protocols supported by the sensor require some type of interface hardware to be
compatible with the serial port found on most personal computers (or USB-to-serial adapters). There are
several SDI-12 interface adapters available in the marketplace; however, METER has not tested any of these
interfaces and cannot make a recommendation as to which adapters work with METER sensors. METER data
loggers and the ZSC and PROCHECK handheld devices can operate as a computer-to-sensor interface for
making on-demand sensor measurements. For more information, please contact Customer Support.

METER SDI12 IMPLEMENTATION

METER sensors use a low-impedance variant of the SDI-12 standard sensor circuit (Figure 2). During the
power-up time, sensors output some sensor diagnostic information and should not be communicated with
until the power-up time has passed. After the power up time, the sensors are compatible with all commands
listed in the SDI-12 Specification v1.3 except for the continuous measurement commands (aR0–aR9 and
aRC0–aRC9) and the concurrent measurement commands (aC–aC9 and aCC0–aCC9). M, R, and C command
implementations are found on pages 8–9.

Out of the factory, all METER sensors start with SDI-12 address 0 and print out the DDI serial startup string
during the power up time. This can be interpreted by non-METER SDI-12 sensors as a pseudo-break condition
followed by a random series of bits.

The ATMOS 41 will omit the DDI serial startup string (sensor identification) when the SDI-12 address is
nonzero.

ATMOS41 INTERNAL MEASUREMENT SEQUENCE

Upon power up, the ATMOS41 initializes an internal timer to 55. This internal timer is incremented by 1 every
second and resets to 0 after incrementing to 59. In addition, issuing an averaging command (aM!, aR0!, aR3!,
aR7!, and aC!) resets this timer to 55.

While powered up, the ATMOS41 continuously counts drops from the precipitation sensor and takes solar
radiation, wind, and air temperature measurements every 10 s at internal timer intervals of 0, 10, 20, 30, 40,
50 and logs these values internally. Orientation, vapor pressure, atmospheric pressure, and relative humidity
are measured every 60 s at the internal timer interval of 4 and logged internally. The aR4! command will output
instantaneous measurements of these parameters.

The aM!, aR0!, aR3!, aR7!, and aC! commands (and subsequent D commands when necessary) will compute
and output the averages, accumulations, or maximums of these measurements (and derived measurements)
and reset internal averaging counters and accumulators. Therefore, it is not necessary to oversample
the ATMOS41 and compute averages, accumulations, and maximums in external data systems. Less
frequent sampling has the additional benefit of decreasing data acquisition systems and ATMOS41 power
consumption. If the aM!, aR0!, aR3!, aR7!, and aC! commands are issued more frequently than 2 times their
measurement interval, the ATMOS41 will not average the measurements and will output instantaneous
values. The ATMOS 41 has four error codes available: general error code −9999, calibrations lost or corrupt

−9992, sensor undervoltage condition −9991, and invalid wind measurement error code −9990.

SDI12 CONFIGURATION

Table1 lists the SDI-12 communication configuration.

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