METER ATMOS 22 User Manual

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ATMOS 22 INTEGRATOR GUIDE

SENSOR DESCRIPTION

The ATMOS22 Ultrasonic Anemometer is designed for continuous monitoring of wind speed and direction (see Measurement Specifications). Ultra-low power consumption and a robust, no moving parts design that prevents errors because of wear or fouling, make the ATMOS22 ideal for long-term, remote installations.

NOTE: The ATMOS22 replaces the DS-2 (discontinued) and the outputs and order are not the same as the DS-2. Any DS-2 replaced by the ATMOS 22 will require data acquisition system reprogramming based on information located in the tech note Integrators replacing

DS-2 with ATMOS 22.

APPLICATIONS

• Weather monitoring

• Microenvironment monitoring

• In-canopy wind measurement

• Spatially distributed environmental monitoring

• Wind profiling

• Crop weather monitoring

• Fire danger monitoring/mapping

• Weather networks

18195-06

7.31.2020

ADVANTAGES

• Robust, no moving parts design

• Small form factor

• 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

PURPOSE OF THIS GUIDE

METER provides the information in this integrator guide to help ATMOS22 Ultrasonic Anemometer 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 1.07 or newer.

Figure 1 ATMOS22 Ultrasonic Anemometer

METER Group, Inc. USA

2365 NE Hopkins Court, Pullman, WA 99163

T +1.509.332.2756 F +1.509.332.5158 E [email protected] W metergroup.com

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SPECIFICATIONS

MEASUREMENT SPECIFICATIONS

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

COMMUNICATION SPECIFICATIONS

Output

SDI-12 communication

PHYSICAL SPECIFICATIONS

Dimensions

Diameter 10 cm (3.94 in)

Height 16 cm (6.30 in), includes rain

gauge filter

Operating Temperature Range

Minimum –50 °C

Typical NA

Maximum 60 °C

Wind Direction

Range 0° –359°

Resolution 1°

Accuracy ±5°

Tilt

Range –90° to 90°

Resolution 0.1°

Accuracy ±1°

Data Logger Compatibility

METER ZL6, Em50, and EM60 data loggers or any data acquisition systems capable of 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

ELECTRICAL AND TIMING CHARACTERISTICS

Supply Voltage (VCC to GND)

Minimum 3.6 VDC continuous

Typical NA

Maximum 15.0 VDC continuous

NOTE: The ATMOS 22 must be continuously powered to workproperly.

NOTE: For the ATMOS 22 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 22 to meet digital logic 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

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Power (brown)

GND

Current Drain (during measurement)

Minimum 0.2 mA

Typical 8.0 mA

Maximum 33.0 mA

Power Up Time (SDI-12, DDI disabled)

Minimum NA

Typical 200 ms

Maximum NA

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 130 ms

Maximum NA

Measurement Duration

Minimum NA

Typical 110 ms

Maximum 3,000 ms

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22 to a logger. Figure 2 provides a low-impedance variant of the recommended SDI-12 Specification v1.3.

PIGTAIL CABLE

GND

DATA

Ground (bare)

Digital communication (orange)

510

NOTE: Some early ATMOS22 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

Figure 2 Equivalent circuit diagram

100K

220PF

Figure 3 Connection types

Ground Digital communication Power

SAFETY 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.

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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 traveling between the ATMOS 22 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 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 to 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22 is set to address 0, a DDI serial string is sent on power up, identifying the sensor.

INTERFACING THE SENSOR TO A COMPUTER

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 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 NORTH AMERICA.

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). M, R, and C command implementations are found on page 7.

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22 will omit the DDI serial startup string (sensor identification) when the SDI-12 address is nonzero. Changing the address to a nonzero address is recommended for this reason.

ATMOS22 INTERNAL MEASUREMENT SEQUENCE

Upon power up, the ATMOS 22 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!, and aC!) resets this timer to 55.

While powered up, the ATMOS 22 takes 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 is measured every 60 s at the internal timer interval of 4 and logged internally. The aR4! command will output instantaneous measurements of theseparameters.

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The aM!, aR0!, aR3!, 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 22 and compute averages, accumulations, and maximums in external data systems. Less frequent sampling has the additional benefit of decreasing data acquisition systems and ATMOS 22 power consumption. If the aM!, aR0!, aR3!, and aC! commands are issued more frequently than 2 times their measurement interval, the ATMOS22 will not average the measurements and will output instantaneous values. The ATMOS 22 has two error codes available—general error code –9999 and invalid wind measurement error code –9990.

SDI12 CONFIGURATION

Table1 lists the SDI-12 communication configuration.

Table1 SDI-12 communication configuration

Baud Rate

Start Bits

Data Bits

Parity Bits

Stop Bits

Logic Inverted (active low)

1,200

7 (LSB first)

1 (even)

SDI12 TIMING

All SDI-12 commands and responses must adhere to the format in Figure 4 on the data line. Both the command and response are preceded by an address and terminated by a carriage return line feed combination and follow the timing shown in Figure 5.

START STOPD0 D1 D2 D3 D4 D5 D6 EP

Figure 4 Example SDI-12 transmission of the character 1 (0x31)

SENSORDATA LOGGER

Break

(at least 12 ms)

Command Response

Marking

(at least 8.33 ms)

Figure 5 Example data logger and sensor communication

Marking

(at least 8.33 ms)

Maximum time*Sensor must respond

within 15 ms

*Maximum time is dependent upon the amount of data returned for the command sent.

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COMMON SDI12 COMMANDS

This section includes tables of common SDI-12 commands that are often used in an SDI-12 system and the corresponding responses from METER sensors.

IDENTIFICATION COMMAND aI!

The Identification command can be used to obtain a variety of detailed information about the connected sensor. An example of the command and response is shown in Example 1, where the command is in bold and the response follows the command.

Example 1 1I!113METER␣ ␣ ␣ATM22␣100631800001

Fixed

Parameter

1I!

1 1 Sensor address

13 2 Indicates that the target sensor supports SDI-12 Specification v1.3

METER␣ ␣ ␣ 8 Vendor identification string

ATM22␣ 6 Sensor model string

Character

Length Description

3 Data logger command

Request to the sensor for information from sensor address 1.

Prepended on all responses, this indicates which sensor on the bus is returning the following information.

(METER and three spaces ␣ ␣ ␣ for all METER sensors)

This string is specific to the sensor type. For the ATMOS 22, the string is ATM22 ␣.

100 3 Sensor version

This number divided by 100 is the METER sensor version (e.g., 100 is version 1.00).

631800001 ≤13,

variable

Sensor serial number This is a variable length field. It may be omitted for older sensors.

CHANGE ADDRESS COMMAND aAB!

The Change Address command is used to change the sensor address to a new address. All other commands support the wildcard character as the target sensor address except for this command. All METER sensors have a default address of 0 (zero) out of the factory. Supported addresses are alphanumeric (i.e., a–z, A–Z, and 0–9). An example output from a METER sensor is shown in Example 2, where the command is in bold and the response follows the command.

Example 2 1A0!0

Fixed

Character

Parameter

1A0!

0 1 New sensor address.

Length Description

4 Data logger command.

Request to the sensor to change its address from 1 to a new address of 0.

For all subsequent commands, this new address will be used by the target sensor.

ADDRESS QUERY COMMAND (?!)

While disconnected from a bus, the Address Query command can be used to determine which sensors are currently being communicated with. Sending this command over a bus will cause a bus contention where all the sensors will respond simultaneously and corrupt the data line. This command is helpful when trying to isolate a failed sensor. Example 3 shows an example of the command and response where the command is in bold and the response follows the command. The question mark (?) is a wildcard character that can be used in place of the address with any command except the Change Address command.

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Example 3 ?!0

Parameter

Fixed

Character

Length Description

2 Data logger command.

Request for a response from any sensor listening on the data line.

1 Sensor address.

Returns the sensor address to the currently connected sensor.

COMMAND IMPLEMENTATION

The following tables list the relevant Measurement (M), Continuous (R), and Concurrent (C) commands and subsequent Data (D) commands when necessary.

MEASUREMENT COMMANDS IMPLEMENTATION

Measurement (M) commands are sent to a single sensor on the SDI-12 bus and require that subsequent Data (D) commands are sent to that sensor to retrieve the sensor output data before initiating communication with another sensor on the bus.

Please refer to Table2 and Table3 for an explanation of the command sequence and see Table9 for an explanation of response parameters.

Table2 aM! command sequence

Command Response

This command reports average or maximum values.

aM!

aD0!

aD1! a±<airTemperature>

NOTE: The measurement and corresponding data commands are intended to be used back to back. After a measurement command is processed by the sensor, a service request a <CR><LF> is sent from the sensor signaling the measurement is ready. Either wait until ttt seconds have passed or wait until the service request is received before sending the data commands. See the SDI-12 Specifications v1.3 document for more information.

atttn

a+<windSpeed>+<windDirection>+<gustWindSpeed>

Table3 aM1! command sequence

Command Response

This command reports instantaneous values.

aM1!

aD0!

atttn

a±<xOrientation>±<yOrientation>+<nullValue>

CONTINUOUS MEASUREMENT COMMANDS IMPLEMENTATION

Continuous (R) measurement commands trigger a sensor measurement and return the data automatically after the readings are completed without needing to send a D command.

The aR3! and aR4! commands must be used at intervals of 10s or greater for the response to be returned within 15 ms as defined in the SDI-12 standard.

Please refer to Table4 through Table7 for an explanation of the command sequence and see Table9 for an explanation of response parameters.

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Table4 aR0! measurement command sequence

Command Response

This command reports average or maximum values.

aR0!

NOTE: This command does not adhere to the SDI-12 response timing. See METER SDI-12 Implementation for more information.

a+<windSpeed>+<windDirection>+<gustWindSpeed>±<airTemperature>±<xOrientation>± <yOrientation>+<nullValue>±<NorthWindSpeed>±<EastWindSpeed>

Table5 aR1! measurement command sequence

Command Response

This command reports instantaneous values.

aR1!

NOTE: This command does not adhere to the SDI-12 response timing. See METER SDI-12 Implementation for more information.

a±<xOrientation>±<yOrientation>±<nullValue>

Table6 aR3! measurement command sequence

Command Response

This command reports average or maximum values.

Do not issue this command more frequently than every 20 s or else the ATMOS22 measurements may be compromised. Please see

ATMOS22 Internal Measurement Sequence for more details.

aR3!

NOTE: This command does not adhere to the SDI-12 response format. However, it does adhere to SDI-12 timing if it is sent at intervals ≥10 s. The values in this command are space delimited. As such, a + sign is not assigned between values, and a - sign is only present if the value is negative. See METER SDI-12 Implementation for more information.

a<TAB><NorthWindSpeed> <EastWindSpeed> <gustWindSpeed> <airTemperature> <xOrientation> <yOrientation> <nullValue><CR><sensortype><Checksum><CRC>

Table7 aR4! measurement command sequence

Command Response

This command reports instantaneous values.

aR4!

NOTE: This command does not adhere to the SDI-12 response for mat. The values in this command are space delimited. As such, a + sign is not assigned between values, and a - sign is only present if the value is negative. See METER SDI-12 Implementation for more information.

a<TAB><NorthWindSpeed> <EastWindSpeed> <gustWindSpeed> <airTemperature> <xOrientation> <yOrientation> <nullValue><CR><sensortype><Checksum><CRC>

CONCURRENT MEASUREMENT COMMANDS IMPLEMENTATION

Concurrent (C) measurement commands are typically used with sensors connected to a bus. Measurements are initiated with a C command and subsequent D commands are sent to the sensor to retrieve the readings.

Please refer to Table8 for an explanation of the command sequence and Table9 for an explanation of response parameters.

Table8 aC! measurement command sequence

Command Response

This command reports average or maximum values.

Please see ATMOS22 Internal Measurement Sequence for more details.

aC!

aD0! a+<windSpeed>+<windDirection>+<gustWindSpeed>

aD1! a±<airTemperature>

aD2! a±<xOrientation>±<yOrientation>+<nullValue>

aD3! a±<NorthWindSpeed>±<EastWindSpeed>+<gustWindSpeed>

NOTE: Please see the SDI-12 Specifications v1.3 document for more information.

atttnn

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PARAMETERS

Table9 Parameter Descriptions

Parameter Unit Description

— Positive or negative sign denoting sign of the next value

ttt

<TAB>

<CR>

<LF>

— SDI-12 address

— Number of measurements (fixed width of 1)

— Number of measurements with leading zero if necessary (fixed width of 2)

s Maximum time measurement will take (fixed width of 3)

— Tab character

— Carriage return character

— Line feed character

m/s Wind speed from the northerly direction (negative values denote southerly direction)

(average since the last measurement or instantaneous value depending on SDI-12 command used)

m/s Wind speed from the easterly direction (negative values denote westerly direction)

(average since the last measurement or instantaneous value depending on SDI-12 command used)

m/s Combined wind speed magnitude of the <NorthWindSpeed> and <EastWindSpeed> (average

since the last measurement or instantaneous value depending on SDI-12 command used)

m/s Maximum measured <windSpeed> since the last measurement

° Wind heading clockwise from north reference

(average since the last measurement or instantaneous value depending on SDI-12 command used)

°C Air temperature (not a true air temperature as it is not corrected for solar radiation)

(average since the last measurement or instantaneous value depending on SDI-12 command used)

X orientation angle (0 is level) (last measured value)

Y orientation angle (0 is level) (last measured value)

— This parameter is reported as 0. Previous firmware versions reported a compass heading,

which has been removed.

— ASCII character denoting the sensor type

For ATMOS 22, the character is the right square bracket ] character

— METER serial checksum

<CRC>

— METER serial 6-bit CRC

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SERIAL CHECKSUM

These checksums are used in the continuous commands R3 and R4. The legacy checksum is computed from the start of the transmission to the sensor identification character, excluding the sensor address.

Legacy checksum example input is <TAB>0.26 1.27 0.37 23.1 3.2 4.8 0<CR>\Hg and the resulting checksum output is H.

uint8_t LegacyChecksum(const char * Response)

{ uint16_t length; uint16_t i; uint16_t sum = 0;

// Finding the length of the response string length = strlen(response);

// Adding characters in the response together for( i = 0; i < length; i++ ) { sum += response[i];

if(response[i] == '\r') { // Found the beginning of the meta data section of the response break; } }

// Include the sensor type into the checksum sum += response[++i];

// Convert checksum to a printable character sum = sum % 64 + 32;

return sum; }

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The more robust CRC6, if available, utilizes the CRC-6-CDMA2000-A polynomial with the value 48 added to the results to make this a printable character and is computed from the start of the transmission to the legacy checksum character, excluding the senor address.

CRC6 checksum example input is <TAB>0.26 1.27 0.37 23.1 3.2 4.8 0<CR>\Hg and the resulting checksum is the character g.

unit8_t CRC6_Offset (const char *buffer)

{ uint16_t byte; uint16_t i; uint16_t bytes; uint8_t bit; uint8_t crc = 0xfc; // Set upper 6 bits to 1’s

// Calculate total message length -- updated once the meta data section is found

bytes = strlen(buffer);

// Loop through all the bytes in the buffer for(byte = 0; byte < bytes; byte++) { // Get the next byte in the buffer and XOR it with the crc crc ^= buffer[byte];

// Loop through all the bits in the current byte for(bit = 8; bit > 0; bit--) { // If the uppermost bit is a 1... if(crc & 0x80) { // Shift to the next bit and XOR it with a polynomial crc = (crc << 1) ^ 0x9c; } else { // Shift to the next bit crc = crc << 1; } }

if(buffer[byte] == '\r') { // Found the beginning of the meta data section of the response

// both sensor type and legacy checksum are part of the crc6 // this requires only two more iterations of the loop so reset "bytes" // bytes is incremented at the beginning of the loop, so 3 is added

bytes = byte + 3; } }

// Shift upper 6 bits down for crc crc = (crc >> 2);

// Add 48 to shift crc to printable character avoiding \r \n and ! return (crc + 48); }

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