WIKA Transmitter (GDHT-20)

For density, temperature, pressure and moisture of insulation gases, with Modbus® output


  • Permanent monitoring of the relevant gas condition parameters in closed tanks
  • For internal and external SF6-insulated equipment

Special Features

  • High-accuracy sensor technology
  • Modbus® output protocol via RS-485 interface
  • Ingress protection IP65
  • Very good long-term stability and EMC characteristics
  • Compact dimensions

Sales Contact (Wika.sales@asyatrafo.com)




The model GDHT-20 transmitter is a multi-sensor system with digital output for the measurands of pressure, temperature and humidity. Based on these measured values, the condition-related data can be determined.

Permanent monitoring
In order to prevent system failures in switchgear and, with that, network outages, the permanent monitoring of the gas density and moisture content is essential.

The GDHT-20 transmitter calculates the current gas density from the pressure and temperature using a complex virial equation in the transmitter’s powerful microprocessor. Changes in pressure resulting from thermal effects will be compensated by this and will not affect the output value.

In addition, the GDHT-20 transmitter delivers humidity or dew point information, which enables monitoring within the terms of the Cigré directives and IEC standards.

Modbus® field bus
The RS-485 interface communicates using the Modbus® RTU protocol. The instrument’s output parameters and their units can be configured and read according to requirements. The GDHT-20 transmitter can be freely configured in percentage values by the user for any defined gas mixture consisting of SF6, N2, CF, O2, CO2, 3M™ Novec™ 4710, He and Ar. The calculation of gas density is based on the partial pressure method of the individual gas components.
The humidity values can be output for SF6 gas and N2.

Signal stability
Due to its high long-term stability, the transmitter is maintenance-free and requires no recalibration.
Due to the hermetically sealed weld seam and a measuring cell design without sealing elements, the permanent sealing of the measuring cell is ensured.


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