Meter Hydros 21 topic

Introduction

A compact 3.4 cm diameter sensor that fits into tight spaces, the HYDROS 21 is a low-cost, durable, and easy-to-use tool for monitoring EC, temperature, and depth in both groundwater and surface water.

The Hydros 21 is implemented as a sub-classes of the SDI12Sensors class. It requires 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.

Sensor Datasheet

Documentation for the SDI-12 Protocol commands and responses for the Hydros 21 can be found at: http://library.metergroup.com/Manuals/13869_CTD_Web.pdf

Build flags

Sensor Constructor

Example Code

The Meter Hydros21 is used in the menu a la carte example.

Classes

class MeterHydros21

The Sensor sub-class for the Meter Hydros 21 conductivity, temperature, and depth sensor.

class MeterHydros21_Cond

The Variable sub-class used for the conductivity output from a Meter Hydros 21 3-in-1 water level sensor..

class MeterHydros21_Temp

The Variable sub-class used for the temperature output from a Meter Hydros 21 3-in-1 water level sensor..

class MeterHydros21_Depth

The Variable sub-class used for the depth output from a Meter Hydros 21 3-in-1 water level sensor..

Sensor Variable Counts

The number of variables that can be returned by the Meter Hydros 21

#define HYDROS21_NUM_VARIABLES = 3

Sensor::_numReturnedValues; the Hydros 21 can report 3 values.

#define HYDROS21_INC_CALC_VARIABLES = 0

Sensor::_incCalcValues; we don't calculate any additional values.

Sensor Timing

The sensor timing for a Meter Hydros 21

#define HYDROS21_WARM_UP_TIME_MS = 500

Sensor::_warmUpTime_ms; maximum warm-up time in SDI-12 mode: 500ms.

#define HYDROS21_STABILIZATION_TIME_MS = 0

Sensor::_stabilizationTime_ms; the Hydros 21 is stable as soon as it warms up (0ms stabilization).

#define HYDROS21_MEASUREMENT_TIME_MS = 1000

Sensor::_measurementTime_ms; maximum measurement duration: 1000ms.

#define HYDROS21_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 Hydros 21 requires no extra time.

Conductivity

The conductivity variable from a Meter Hydros 21

• Range is 0 – 120 mS/cm (bulk)
• Accuracy is ±0.01mS/cm or ±10% (whichever is greater)

#define HYDROS21_COND_RESOLUTION = 1

Decimals places in string representation; conductivity should have 1.

#define HYDROS21_COND_VAR_NUM = 2

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

#define HYDROS21_COND_VAR_NAME = "specificConductance"

Variable name in ODM2 controlled vocabulary; "specificConductance".

#define HYDROS21_COND_UNIT_NAME = "microsiemenPerCentimeter"

Variable unit name in ODM2 controlled vocabulary; "microsiemenPerCentimeter" (µS/cm)

#define HYDROS21_COND_DEFAULT_CODE = "Hydros21cond"

Default variable short code; "Hydros21cond".

Temperature

The temperature variable from a Meter Hydros 21

• Range is -11°C to +49°C
• Accuracy is ±1°C

#define HYDROS21_TEMP_RESOLUTION = 2

Decimals places in string representation; temperature should have 2.

#define HYDROS21_TEMP_VAR_NUM = 1

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

#define HYDROS21_TEMP_VAR_NAME = "temperature"

Variable name in ODM2 controlled vocabulary; "temperature".

#define HYDROS21_TEMP_UNIT_NAME = "degreeCelsius"

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

#define HYDROS21_TEMP_DEFAULT_CODE = "Hydros21temp"

Default variable short code; "Hydros21temp".

Water Depth

The water depth variable from a Meter Hydros 21

• Range is 0 to 5 m or 0 to 10 m, depending on model
• Accuracy is ±0.05% of full scale

#define HYDROS21_DEPTH_RESOLUTION = 1

Decimals places in string representation; depth should have 1.

#define HYDROS21_DEPTH_VAR_NUM = 0

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

#define HYDROS21_DEPTH_VAR_NAME = "waterDepth"

Variable name in ODM2 controlled vocabulary; "waterDepth".

#define HYDROS21_DEPTH_UNIT_NAME = "millimeter"

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

#define HYDROS21_DEPTH_DEFAULT_CODE = "Hydros21depth"

Default variable short code; "Hydros21depth".

Define documentation