ModularSensors > Modules > Supported Sensors > SDI-12 Sensors > Meter Teros 11

Meter Teros 11 module

Classes for the Meter Teros 11 soil moisture probe.

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

MeterTeros11(char SDI12address, int8_t powerPin, int8_t dataPin, uint8_t measurementsToAverage = 1)

Construct a new Meter Teros 11 object.

Parameters
SDI12address The SDI-12 address of the Teros 11; can be a char, char*, or int.
powerPin

The pin on the mcu controlling power to the Teros 11 Use -1 if it is continuously powered.

  • The Teros 11 requires a 3.5-12V power supply, which can be turned off between measurements
dataPin The pin on the mcu connected to the data line of the SDI-12 circuit.
measurementsToAverage The number of measurements to take and average before giving a "final" result from the sensor; optional with a default value of 1.

The SDI-12 address of the sensor, the Arduino pin controlling power on/off, and the Arduino pin sending and receiving data are required for the sensor constructor. Optionally, you can include a number of distinct readings to average. The data pin must be a pin that supports pin-change interrupts.



Example Code

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

#include <sensors/MeterTeros11.h>

const char*   teros11SDI12address = "4";  // The SDI-12 Address of the Teros 11
const int8_t  terosPower = sensorPowerPin;  // Power pin (-1 if unconnected)
const int8_t  terosData  = 7;               // The SDI12 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");

Classes

class MeterTeros11
The Sensor sub-class for the Meter Teros 11 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_Temp
The Variable sub-class used for the temperature output output from a 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 = 3
Sensor::_numReturnedValues; the Teros 11 can report 3 values.

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.

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

MeterTeros11_Ea(MeterTeros11* parentSense, const char* uuid = "", const char* varCode = TEROS11_EA_DEFAULT_CODE) explicit

Construct a new MeterTeros11_Ea object.

Parameters
parentSense The parent MeterTeros11 providing the result values.
uuid A universally unique identifier (UUID or GUID) for the variable; optional with the default value of an empty string.
varCode A short code to help identify the variable in files; optional with a default value of "SoilEa".

#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 = 0
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".

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

MeterTeros11_Temp(MeterTeros11* parentSense, const char* uuid = "", const char* varCode = TEROS11_TEMP_DEFAULT_CODE) explicit

Construct a new MeterTeros11_Temp object.

Parameters
parentSense The parent MeterTeros11 providing the result values.
uuid A universally unique identifier (UUID or GUID) for the variable; optional with the default value of an empty string.
varCode A short code to help identify the variable in files; optional with a default value of "SoilTemp".

#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".

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

MeterTeros11_VWC(MeterTeros11* parentSense, const char* uuid = "", const char* varCode = TEROS11_VWC_DEFAULT_CODE) explicit

Construct a new MeterTeros11_VWC object.

Parameters
parentSense The parent MeterTeros11 providing the result values.
uuid A universally unique identifier (UUID or GUID) for the variable; optional with the default value of an empty string.
varCode A short code to help identify the variable in files; optional with a default value of "SoilVWC".

#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 = 2
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".