Delta-T Devices Ltd.

- Model GP1 - General Purpose Data Logger


The GP1 Data Logger is a complete logging solution housed in a waterproof IP67 enclosure with battery power. The internal memory can hold >600,000 readings - more than enough for one year's operation (typical).

  • High accuracy 7 channel data logger
  • 600,000 readings
  • Free use of DeltaLINK-Cloud data sharing service
  • Smart relay control

The GP1 can log up to:

  • 2 differential analogue voltages
  • 2 temperature channels
  • 2 pulse counters

As well as being a powerful general purpose logger, the GP1 is ideal for soil moisture applications and can log:

  • 2 soil moisture sensors e.g. ThetaProbes, SM300s or SM150s
  • 2 temperature probes (or 2 further SM150 Sensors)
  • 2 pulse counters (e.g. rainfall or water meter)
  • 1 Delta-TWET Sensor
  • Tensiometer input option using GP-PBA-X50

The optional GP-PBA-X50 Precision Bridge Adapter enables a GP1 to log up to 2 bridge sensors such as pressure transducers and strain gauges and allows for the logging of up to two water-filled tensiometers. The bridge adapter is optimised for use with Delta-T Devices' SWT range of water-filled tensiometers but is compatible with many other bridge sensors.

When connected to 1 or 2 ThetaProbes, SM300 or SM150 Soil Moisture Sensors, the GP1 Logger provides simple high accuracy recording of moisture content (as well as rainfall and temperature).

The GP1 Data Logger, running DeltaLINK Software, can control irrigation directly from the soil moisture (and/or rainfall and/or temperature) or act as a sophisticated interface between these sensors and many types of programmable timer.

Start and Stop control levels can be separately configured and there's even an option for pulsing the output when it's desirable to match the water application rate to the soil's infiltration capacity.

NB: Our GP2 Advanced Data logger and Controller offers even more advanced irrigation control capabilities.

DeltaLINK PC Software
DeltaLINK PC Software is supplied free with all GP1, GP2 and DL6 data loggers. DeltaLINK allows you to set up the logger input channels and recording parameters, check readings from connected sensors, and collect & display data.

  • Clear graphic display
  • Full configuration

Storage, communications and power
1 Mbyte of FLASH memory enables storage of 600K readings (typical). Data can be collected by a laptop locally via RS232 or via USB (USB to RS232 Adaptor Cable type USB-RS232 required), or remotely using the GPRS modem options.

The GP1 has 1 PP3 internal battery as standard. Up to 10 GP1s can share power and communications using an M8 cabling network. GP2 Data Loggers can be integrated into such a network via an adapter cable.


  • Soil Science, Plant Physiology, Agronomy, Climate Research and Meteorology
  • Horticulture, Agriculture, Turf and Gardens-Amenity Landscaping

  • Input connections: 2 voltage channels
    • 2 temperatures or 2additional SM150 orSM300 Sensors [3]
    • 2 counters(33kHz & 50Hz)
    • 1 WET Sensor
  • Control outputs: 1 relay (1A)
  • Readings stored: 600,000
  • Recording rate: 1 second to 24 hours
  • Configuration: DeltaLINK
  • Communication options: RS232 USB [1] or modem
  • Sensor excitation:
    • 1 switched logger power
    • 1 5V precision reference
  • Power: 1 9V 6LR61 (PP3)alkaline or external power 11-24V
  • Battery life (dependent on usage): ~ 1 year
  • Enclosure rating: IP67
  • Temperature range: -20 to +60°C
  • Display: –
  • Size: 140 x 105 x 45mm
  • Typical applications:
    • Monitoring soil moisture
    • General data logging
    • Controlling irrigation

Sensor compatibility (maximum number of sensors that could be connected [2]

  • ML3: (2) with temp (4) excl. temp [3]
  • SM150T: (2) with temp (4) excl. temp [3]
  • PR2
  • PR2 SDI-12
  • WET Sensor: (1)
  • EQ3: (2 as mV only)
  • Temperature: (2)
  • Tensiometers: (2) each requires GP-PBA-X50
  • Counters or Events: (2) 1 fast 1 slow
  • Relay Output: (1)

[1] With USB to RS232 Adapter Cable type USB-RS232
[2] With appropriate expansion cards and power supply arrangements
[3] Temp channels provide only single-ended inputs so should not be used with long cables or in noisy environments when used with soil moisture sensors. The accuracy ?gures quoted for GP1 soil moisture readings do not apply to these resistance channels when con?gured as soil moisture inputs.