GP2 Data Logger and Controller

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GP2 Data Logger and ML3 ThetaProbeGP2 Data LoggerGP2 Data Logger and ControllerUse of SDI-12 Sensors with GP2_cable reversed – NTP plus STP1


"Working with Delta‐T Devices, we installed two arrays of SM150T soil moisture sensors at varying depths ‐ in selected well‐managed plantations in the Santa Marta region of Colombia. We also installed a WS‐GP2 Weather Station (based around the GP2 Advanced Data Logger and Controller) to provide input data to drive our irrigation model ‐ as there is limited agrometeorological recording in the region. The Delta‐T Devices kit has been first class ‐ it has not missed a beat since we installed the equipment." Prof Jerry Knox
Cranfield Water Science Institute,
Cranfield University, UK
"“Having access to real-time data on compost moisture content and the environmental conditions in the glasshouse has enabled us to impose exactly the right degree of water deficit stress at the optimum stage of plant development. The next step is to use the Delta-T Devices GP2 system to apply both precision irrigation and deficit irrigation automatically at different stages of crop development. Next year we aim to produce 40,000 plants in this way”." Dr Mark Else
Head of Department - Crop Science and Production Systems, NIAB EMR
"A major advantage of the GP2 Data Logger is that up to 12 moisture sensors can be monitored concurrently. This enables us to easily position multiple sensors in strategic locations across the cropping area - to help account for the inherent variability in soft fruit growing systems." Mike Davies, Science Project Leader
NIAB EMR (East Malling Research)
  • Ideal for demanding irrigation and fertigation applications
  • Monitor soil moisture and other key growing conditions
  • Directly control irrigation using-on board relays

The GP2 Data Logger is a powerful monitoring and control solution for irrigation and fertigation – enabling simple or sophisticated models and multiple zone control (up to 6 relays). It has 12 differential (or 24 single ended) channels.

DeltaLINK‐Cloud – online data viewing and sharing platform

SDI‐12 enabled

Precision Irrigation

The GP2 is ideal for running precision soil moisture sensor controlled irrigation systems. These systems automatically maintain the correct levels of moisture for optimal plant growth – leading to improved yield and quality.

Find out more by clicking the relevant buttons below to download posters:












WHITE PAPER – Vapour Pressure Deficit

“Soil moisture responses to vapour pressure deficit in polytunnel-grown tomato under soil moisture triggered irrigation control”. Download it here

WHITE PAPER – Substrate Temperature Correction

“Temperature correction of substrate moisture measurements made in coir”. Download it here

The Benefits of Precision Irrigation

The GP2 can control irrigation using combined sensor inputs.
Benefits from optimising crop irrigation can include:

  • Reduction in water use
  • Applying less fertiliser – reduced run-off and environmental impact
  • Lower energy costs for pumping water
  • Compliance with national and international regulations
  • Positive effect on plant growth and development – improved quality
  • Saving in labour costs (e.g. less pruning)
  • Increased profits

Flow Aid Project

Delta-T Devices was extensively involved in the 3 year EU funded Flow Aid Project. The aim of this project was to find new approaches to irrigation scheduling and farm management in Mediterranean countries where the supply or quality of water is low. Delta-T Devices soil moisture sensors and data loggers were used at the test sites to schedule irrigation in response to the water requirements of plants.

Script Editor Feature

The new Script Editor allows creations of step by step operations to control simple or complex processes, or recording requirements. It can also implement models, useful in areas such as disease prediction or multi-zone irrigation.

This degree of sophistication, including the ability to apply PID control, means the potential applications are numerous and varied.

The editor interface is easy to use – no programming language is involved.




Input connections 12 differential (or 24 single-ended) analog inputs configurable as: Voltage, Resistance (12 3-wire or 24 2-wire), Bridge (12), Potentiometer (12) 4 digital inputs as: Counters, (2 fast + 2 slow), Frequency, Digital state 1 Delta-T WET sensor channel Unlimited virtual channels Serial input channel: 62 SDI-12 sensors or a single WET Sensor
Control outputs 2 relay outputs expandable to 6 (1 A)
Readings stored 2.5 Million
Recording rate 1 second to >24 hours
Configuration DeltaLINK
Communication options SDI-12, USB, RS232, ethernet or modem
Sensor excitation Calibrated 3 V reference, +5 V and +12 V regulated, or 5 to 10.5 V (battery or external power), user selectable
Power 6 AA alkaline batteries or external power 10-15 V DC
Battery life (dependent on usage) >310K readings, lasting 530 days
Enclosure rating IP65
Temperature range -20 to +60°C
Size 225 x 185 x 75 mm
Typical applications Demanding research projects
Environmental monitoring
Varied control applications
Sensor compatibility (maximum number of sensors that could be connected [1]
WET150 ✓ (62)
ML3 ✓ (6) with temp / (12) without temp
SM150T ✓(6) with temp / (12) without temp
PR2 ✓(2 PR2/6) (3 PR2/4)
PR2 SDI-12 ✓ (50) PR2/6 ✓ (62) PR2/4
WET Sensor ✓ (1)
EQ3 ✓ 6 with temp / 12 without temp
Temperature ✓ (12)
Tensiometers ✓ (12)
Counters or Events ✓ (4) 2 fast 2 slow
Relay Output ✓(2) expandable to (6)
  [1] With appropriate expansion cards and power supply arrangements   For full GP2 specification please see the GP2 data sheet

Product Resources

Additional resources can be found at the GP2 and DeltaLINK Resource Centre. The Resource Centre contains a wide range of application information and tutorials – covering irrigation control, evapotranspiration, vapour pressure deficit, and much more.

Data Sheets

Case Studies




Technical Notes

Advanced features of the new GP2 Data Logger and Controller

  • Powerful, yet highly accessible Script Editor
  • Virtual Channels
  • Unique Simulator function
  • Smart irrigation and fertigation
  • PID control
  • Model implementation, simulation and evaluation
  • Evapotranspiration calculation and analysis

Customised control (simple or advanced)

Control conditions for experiments and applications can range from simple thresholding to sophisticated calculations using the Script Editor. Control parameters (e.g. target soil moisture level) can be adjusted without interrupting data logging.

Script Editor

The GP2 is a flexible and powerful research and control instrument – enabling model implementation, simulation and evaluation. The new Script Editor is easy to use, yet allows the creation of complex functions such as disease prediction, degree days, dew point, wind chill factor, PID control, and evapotranspiration calculation and analysis.

  • Script Editor creates sequences of operations to implement models
  • Advanced control and recording capabilities
  • Easy user interface: no typing out of commands; no programming language
  • Implement simple or complex conditions, algebraic expressions and record result values
  • Create and manipulate variables e.g. for disease risk factor

This powerful software feature creates step by step operations to control simple or complex processes or recording requirements. The editor interface is easy to use – no programming language is involved. It can also implement models, useful in areas such as disease prediction or multi-zone irrigation. This degree of sophistication, including the ability to apply PID control, means the potential applications are numerous and varied.

Virtual channels

Calculations based on the measurements from several input channels can be recorded and displayed as additional “virtual channels”.


  • Test and optimise logging programs using the built-in Simulator.
  • Simulate how the program responds to changes in weather data, irrigation systems and soil moisture movement etc.

This unique software feature allows logging programs to be tested before real-world activation. For applications involving weather data, irrigation or soil moisture recording, the environmental variables can be changed to test how the program responds. Years of logging time can be simulated in just a few minutes.

Typical examples of advanced control and modelling

PID ControlThe GP2 is a powerful research tool for experimental research. The powerful new Script Editorfunction gives the user an accessible way to create sophisticated mathematical functions and models that can be applied in real-time to the measurement data collected by the GP2. In experimental work detailed here we have created an enhanced PID controller within the DeltaLINK 3.0 Script Editor – enabling the GP2 to deliver precision irrigation control for a Poinsettia plant. The data collected shows precise control of soil moisture levels and the PID controller responding appropriately to the diurnal cycle. The experimental system also includes water flow and radiation sensors. The GP2 collects data from these sensors and calculates daily totals enabling the relationship between solar radiation and water use to be investigated.

Download GP2 PID scientific poster here.
Explanation of PID Control

Evapotranspiration calculation and analysis In this example, the GP2’s Script Editor & Simulator features were used for a comparison of four empirical potential evapotranspiration equations (PET). The Script Editor was used to implement mathematical models (Xu & Singh 2001) that calculated daily average values for air temperature, relative humidity, and solar radiation. These values were then used with empirical models to estimate PET. The results indicate that the solar radiation based models are well grouped and follow a similar trend, whereas the temperature based model (McCloud) appears to overestimate PET.

The empirical PET models described in the poster can be installed into a standard GP2, and with the appropriate sensors, used to calculate real-time estimates of PET. If comparison pan evaporation or lysimeter data is available then the model coefficients can be adjusted on the GP2 to optimise the model for local conditions as outlined by Xu & Singh (2001).

Download GP2 Evapotranspiration scientific poster here.

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