ERHTP SDI-12 Inteface - Parameters and Units
ERHTP Environmental Parameters
Parameter | Unit | Descrption |
air_ temperature | °C / °F | Air temperature (dry-bulb temperature) |
relative_humidity | % | Relative humidity of air |
barometric_pressure | hPa | Barometric pressure |
sea_level_pressure | hPa | Reduced to sea level atmospheric pressure |
dew_point | °C | Dew point (Dew temperature) |
absolute_humidity | g/m3 | Absolute humidity of air |
vapor_pressure | hPa | Vapor pressure in humid air |
saturated_vapor_pressure | hPa | Saturated vapor pressure in humid air |
heat_index | °C | Physiological heat index in humid air |
speed_of_sound | m/s | Speed of sound in humid air |
mixing_ratio | g/kg | Mixing ratio of moisture in air |
specific_enthalpy | kJ/kg | Thermodynamic specific enthalpy of humid air |
| water_activity | - | Water activity in humid air |
water_boiling_point | °C | Boiling point of water |
wet_bulb_temperature | °C | Thermodynamic wet-bulb temperature |
CO2_percentage | % |  RHTP-CO2 version only: concentration (percentage) of CO2 in air |
ERHTP Diagnostic Parameters
Parameter | Unit | Description |
MCU_voltage | mV | Internally regulated voltage supply for the on-board microcontroller |
SEN_voltage | mV | Internally regulated voltage supply for the sensor circuits |
VIN_voltage | mV | Unregulated voltage supply fed to the probe |
MCU_temperature | °C | Temperature of the on-board microcontroller |
MCU errors | - | A register of errors occurred in the MCU of a probe |
reset_cause | - | A register of the most recent MCU reset cause code |
power_errors | - | A register of error in the power circuitry of a probe |
sensor_errors | - | A register of errors occurred during sensing |
errors_count | - | Total count of errors occurred in a probe |
wet_bulb_iterations | - | Count of iterations to solve the equation for wet_bulb_temperature |
break_duration | - | Duration the SDI-12 break symbol generated by the SDI-12 master and
measured by the probe |
NOTE: MCU_errors, power_errors, sensor_errors, errors_count reset to 0 at power-up.
ERHTP On-board Heater Parameters
| Parameter | Unit | Description |
HEAT_mode | - | Indicator of the operational mode of the on-board heater: MANUAL, AUTO |
HEAT_status | - | Indicator of the state of the heater cycle: ON, COOLING, OFF |
HEAT_duty_cycle | - | Automatically set parameter for PWM control of the on-board heater |
HEAT_set_time | s | User-defined ON time for the on-board heater |
HEAT_remaining_time | s | Self-updating remaining ON time for the on-board heater when enabled |
HEAT_initial_temperature | °C | Temperature of the RH-sensor at the beginning of heater’s ON state |
HEAT_delta_temperature | °C | Increase of temperature of the RH-sensor during heating |
COOL_remaining_time | s | Self-updating remaining COOLING time for the RH-sensor after heater
automatically shuts OFF |
COOL_initial_temperature | °C | The temperature of the RH-sensor at the end of heater’s ON stat |
COOL_delata_temperature | °C | Decrease of temperature of the RH-sensor during cooling |
ERHTP Input Parameters
Parameter | Unit | Description |
height_above_sea_level | m | Height of installation point above sea level (for fixed installations only) |
vertical_temp_coeff | °C/100m | Vertical temperature gradient in the atmosphere |
CAL_temperature_A | - | Calibration coefficient A for air temperature |
CAL_temperature_B | - | Calibration coefficient A for air temperature |
CAL_temperature_C | - | Calibration coefficient B for air temperature |
| CAL_temperature_date | - | User-defined date of the most recent air temperature calibration |
TEST_temperature_value | °C/°F | User-defined temperature value for manual test and evaluation of the air
temperature calibration
|
CAL_humidity_A | - | Calibration coefficient A for relative humidity |
CAL_humidity_B | - | Calibration coefficient B for relative humidity |
CAL_humidity_C | - | Calibration coefficient C for relative humidity |
CAL_humidity_date | - | User-defined date of the most recent relative humidity calibration |
TEST_humidity_value | % | User-defined temperature value for manual test and evaluation of the
relative humidity calibration |
CAL_pressure_A | - | Calibration coefficient A for barometric pressure |
CAL_pressure_B | - | Calibration coefficient B for barometric pressure |
CAL_pressure_C | - | Calibration coefficient C for barometric pressure |
CAL_pressure_date | - | User-defined date of the most recent barometric pressure calibration |
TEST_pressure_value | hPa | User-defined temperature value for manual test and evaluation of the
barometric pressure calibration |
Related Articles
Definitions of Physical Parameters
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