Meter Teros 11 module

Introduction

Meter Environmental makes two series of soil moisture sensors, the ECH2O series and the Teros series. This page is for the Teros series.

Both series of sensors operate as sub-classes of the SDI12Sensors class. They require a 3.5-12V power supply, which can be turned off between measurements. While contrary to the manual, they will run with power as low as 3.3V. On the 5TM with a stereo cable, the power is connected to the tip, data to the ring, and ground to the sleeve. On the bare-wire version, the power is connected to the white cable, data to red, and ground to the unshielded cable.

Sensor Datasheet

Documentation for the SDI-12 Protocol commands and responses for the Meter Teros 11 can be found at: http://publications.metergroup.com/Manuals/20587_TEROS11-12_Manual_Web.pdf

Voltage Ranges

• Supply Voltage (VCC to GND), 4.0 to 15.0 VDC
• Digital Input Voltage (logic high), 2.8 to 3.9 V (3.6 typical)
• Digital Output Voltage (logic high), 3.6 typical

Build flags

Sensor Constructor

Example Code

The Meter Teros is used in the menu a la carte example.

#include <sensors/MeterTeros11.h>

// NOTE: Use -1 for any pins that don't apply or aren't being used.
const char*   teros11SDI12address = "4";  // The SDI-12 Address of the Teros 11
const int8_t  terosPower          = sensorPowerPin;  // Power pin
const int8_t  terosData           = 7;               // The SDI-12 data pin
const uint8_t teros11NumberReadings = 3;  // The number of readings to average

// Create a METER TEROS 11 sensor object
MeterTeros11 teros11(*teros11SDI12address, terosPower, terosData,
                     teros11NumberReadings);

// Create the matric potential, volumetric water content, and temperature
// variable pointers for the Teros 11
Variable* teros11Ea =
    new MeterTeros11_Ea(&teros11, "12345678-abcd-1234-ef00-1234567890ab");
Variable* teros11Temp =
    new MeterTeros11_Temp(&teros11, "12345678-abcd-1234-ef00-1234567890ab");
Variable* teros11VWC =
    new MeterTeros11_VWC(&teros11, "12345678-abcd-1234-ef00-1234567890ab");
Variable* teros11Count =
    new MeterTeros11_Count(&teros11, "12345678-abcd-1234-ef00-1234567890ab");

Classes

class MeterTeros11

The Sensor sub-class for the Meter Teros 11 sensor.

class MeterTeros11_Count

The Variable sub-class used for the raw calibrated VWC counts from a Meter Teros soil moisture/water content sensor.

class MeterTeros11_Temp

The Variable sub-class used for the temperature output output from a Teros soil moisture/water content sensor.

class MeterTeros11_Ea

The Variable sub-class used for the apparent dielectric permittivity (εa, matric potential) from a Meter Teros soil moisture/water content sensor.

class MeterTeros11_VWC

The Variable sub-class used for the volumetric water content output from a Teros soil moisture/water content sensor.

Defines

#define TEROS11_NUM_VARIABLES = 4

Sensor::_numReturnedValues; the Teros 11 can report 2 raw values - counts and temperature.

#define TEROS11_INC_CALC_VARIABLES = 2

Sensor::_incCalcValues; We calculate permittivity and water content from the raw counts and temperature reported by the Teros 11.

Sensor Timing

The sensor timing for a Meter Teros 11

#define TEROS11_WARM_UP_TIME_MS = 250

Sensor::_warmUpTime_ms; the Teros 11 warm-up time in SDI-12 mode: 245ms typical.

#define TEROS11_STABILIZATION_TIME_MS = 50

Sensor::_stabilizationTime_ms; the Teros 11 is stable after 50ms.

#define TEROS11_MEASUREMENT_TIME_MS = 50

Sensor::_measurementTime_ms; the Teros 11 takes25 ms to 50 ms to complete a measurement.

#define TEROS11_EXTRA_WAKE_TIME_MS = 0

Extra wake time required for an SDI-12 sensor between the "break" and the time the command is sent. The Terros-11 requires no extra time.

Raw Counts

The raw VWC counts variable from a Meter Teros 11

• Range and accuracy of the raw count values are not specified

#define TEROS11_COUNT_RESOLUTION = 1

Decimals places in string representation; EA should have 1.

#define TEROS11_COUNT_VAR_NUM = 0

Sensor variable number; EA is stored in sensorValues[0].

#define TEROS11_COUNT_VAR_NAME = "counter"

Variable name in ODM2 controlled vocabulary; "counter".

#define TEROS11_COUNT_UNIT_NAME = "count"

Variable unit name in ODM2 controlled vocabulary; "count".

#define TEROS11_COUNT_DEFAULT_CODE = "RawVWCCounts"

Default variable short code; "RawVWCCounts".

Temperature

The temperature variable from a Meter Teros 11

• Range is -40°C to 60°C
• Accuracy is:
  • ± 1°C, from -40°C to 0°C
  • ± 0.5°C, from 0°C to + 60°C

#define TEROS11_TEMP_RESOLUTION = 2

Decimals places in string representation; temperature should have 2.

1 is reported, adding extra digit to resolution to allow the proper number of significant figures for averaging - resolution is 0.1°C

#define TEROS11_TEMP_VAR_NUM = 1

Sensor variable number; temperature is stored in sensorValues[1].

#define TEROS11_TEMP_VAR_NAME = "temperature"

Variable name in ODM2 controlled vocabulary; "temperature".

#define TEROS11_TEMP_UNIT_NAME = "degreeCelsius"

Variable unit name in ODM2 controlled vocabulary; "degreeCelsius" (°C)

#define TEROS11_TEMP_DEFAULT_CODE = "SoilTemp"

Default variable short code; "SoilTemp".

EA

The EA variable from a Meter Teros 11

• Range is 1 (air) to 80 (water)
• Accuracy is:
  • 1–40 (soil range), ±1 εa (unitless)
  • 40–80, 15% of measurement

#define TEROS11_EA_RESOLUTION = 5

Decimals places in string representation; EA should have 5.

4 are reported, adding extra digit to resolution to allow the proper number of significant figures for averaging - resolution is 0.00001

#define TEROS11_EA_VAR_NUM = 2

Sensor variable number; EA is stored in sensorValues[0].

#define TEROS11_EA_VAR_NAME = "permittivity"

Variable name in ODM2 controlled vocabulary; "permittivity".

#define TEROS11_EA_UNIT_NAME = "faradPerMeter"

Variable unit name in ODM2 controlled vocabulary; "faradPerMeter" (F/m)

#define TEROS11_EA_DEFAULT_CODE = "SoilEa"

Default variable short code; "SoilEa".

Volumetric Water Content

The VWC variable from a Meter Teros 11

• Range is:
  • Mineral soil calibration: 0.00–0.70 m3/m3 (0 – 70% VWC)
  • Soilless media calibration: 0.0–1.0 m3/m3 (0 – 100% VWC)
• Accuracy is:
  • Generic calibration: ±0.03 m3/m3 (± 3% VWC) typical in mineral soils that have solution electrical conductivity <8 dS/m
  • Medium specific calibration: ±0.01–0.02 m3/m3 (± 1-2% VWC)in any porous medium

#define TEROS11_VWC_RESOLUTION = 3

Decimals places in string representation; VWC should have 3.

2 are reported, adding extra digit to resolution to allow the proper number of significant figures for averaging - Resolution is 0.001 m3/m3 (0.1% VWC) from 0 – 70% VWC

#define TEROS11_VWC_VAR_NUM = 3

Sensor variable number; VWC is stored in sensorValues[2].

#define TEROS11_VWC_VAR_NAME = "volumetricWaterContent"

Variable name in ODM2 controlled vocabulary; "volumetricWaterContent".

#define TEROS11_VWC_UNIT_NAME = "percent"

Variable unit name in ODM2 controlled vocabulary; "percent" - volumetric percent water content (%, m3/100m3)

#define TEROS11_VWC_DEFAULT_CODE = "SoilVWC"

Default variable short code; "SoilVWC".