Transmitters with inputs for thermocouple temperature sensors

20 Series

GS21 / 4 and GD21 / 4

Socket(s) for K/T thermocouples (-200 to +200°C). Ideal for low temperatures and liquid nitrogen storage vessels.

'D' Indicates LCD display. Last digit indicates number of inputs.


The GenII M series retains the standard GenII transmitter specification and adds 12,000 readings of built-in backup memory. The memory is used in continuous overwrite mode. This means many weeks of data can be held in the transmitter, depending on the number of channels in use.


GD24 with visual and delayed audible alarm (High and Low alarm level can be set in the Darca software). With display.


Sockets for 4 x K (-200 to +1200°C) / N (-200 to +1300°C) thermocouples. With display.


Sockets for 4 x R thermocouples (-200 to +2000°C). With display.


Sockets for 4 x K/T thermocouples (-200 to +200°C) with relay galvanic isolation.




If you require sensors, please order them separately.


WBG Wall bracket docking kit

This kit enables fitment of the transmitter's built-in wall bracket to difficult or uneven surfaces. The kit provides additional docking security.

The following products are supported:

  • All GD, GC, GL and GS series transmitters
  • RP250GD repeater and RC250 receiver


Transmitter Specification

Model(s) Sensors Range Resolution Accuracy *
GS21/GD21 1 x external T or K type thermocouple temperature -200 to 200°C 0.1°C / 0.2°C ±0.3°C
GS24/GD24 4 x external T or K type thermocouple temperature / state inputs
GD21AL/GD24AL As GD21/GD24 with audible and visual alarm.
GD24HV 4 x external T or K type thermocouple temperature      
GD24H 4 x external K/N type thermocouple temperature -200 to 1200°C 0.5°C ±2.0°C
GD24R 4 x external R type thermocouple temperature -200 to 2000°C    
* Please note that the accuracy specifiation quoted does not include the accuracy of the probe that is chosen for use.

Common GenII Transmitter Specification

RF specification: EN300-220
RF power: 10mW
Environment specification  
  Compliant to EN300-220: -10 to +55°C
  Actual: -30 to +65°C
  Humidity: 100% non condensing
Environmental rating: IP40
Dimensions (footprint): 78 x 41mm
Transmission interval range: 1 sec to 4 hours
Indicator (red LED): transmit active/on/off
Control switch (concealed): test mode / hibernate
Antenna socket: SMA


Common to all transmitters

Gen II Quick Start Instructions

Specific to this family of transmitters


ELCC (a sensor for detecting the failure of AC mains supply)
GenII M Series transmitters with backup memory