There are 12 direct sensor inputs on the iMetos3.3 board, supporting up to 600 sensors units.

Main sensors:

Some sensors have to be connected to specific inputs dedicated to them:

  • WIND: wind speed sensor
  • LEAF: leaf wetness sensor
  • RAIN: rain gauge
  • HC2 (two inputs): hygroclip sensors (air temperature and relative humidity)
  • SWITCH input: any switch-type sensor can be connected (e.g. another leaf wetness sensor, tilt sensor, a presostat...).
  • REED input: any reed-type sensor  can be connected (e.g. another rain gauge, flow counter, tilt sensor ...)

Sensors connected to these inputs as well as the battery and solar panel voltage measurement are referred to as “main” sensors.


INPUT 1-4:

INPUT 1-4 can be used for connecting either

1.      Individual sensors (any of the complete range of PI_duty_sensors: Global radiation, temperature, wind direction, barometric pressure, water level, weighting cells....)

2.      PI_bus chains of modules with sensors.

On these inputs, the type of a connected sensor (or whether a chain is connected) is automatically recognized based on Pessl Instruments proprietary chain protocol.

Different temperature sensors are based on the same IC and consequently the iMetos3.3 does not distinguish among them. Therefore default inputs have been reserved for each of this temperature sensors as follows:

  • INPUT 1: air temperature
  • INPUT 2: dry bulb temperature
  • INPUT 3: wet bulb temperature
  • INPUT 4: soil temperature


If a dry bulb temperature happened to be connected to input 4 it will receive the name of “soil temperature” but this will be only the default denomination and the user can change it later without further consequences on FieldClimate.com portal.

Sensors connected directly to the INPUT 1-4 are referred to as “duty-cycle” sensors, because data is transmitted by means of the pulse width. Examples are temperature, global radiation, wind direction, and barometric pressure (complete list is on apendix I).

A PI_bus chain is recognized by its characteristic frequency of 750 Hz. Sensors of the chain are recognized by identifiers (see next page Sensor Identification).In addition to the possible chain inputs on INPUT 1-4, the iMetos3.3 has one dedicated input for chain.                                                                                   

Warning!!    To connect a chain to INPUT 1-4 a 485-to-duty-cycle converter is needed in the connector of the bus (as in previous iMetos boards), the bus cable can’t be connected directly.


Direct chain input:

In addition to the possible chain inputs on INPUT 1-4, the iMetos3.3 has one dedicated input for every chain.


The PI_bus chain input has no need of any 485 to duty converter, the bus cable is connected directly.


Extension connector:

To the extension connector one of the following extensions can be connected:

  • Extension board for two more dedicated chain inputs (chain diplexor or splitter)
  • Extension board for RadioNode (Wireless Sensor Network)
  • Extension board for sensors using the SDI-12 protocol: several Sentec sensors (e.g. Drill and Drop, Aquacheck and Decagon sensors)