WIKA Hybrid Gas Density Monitor (GDM-100-T)

With Modbus® or analogue 4 … 20 mA output signal


  • Medium and high-voltage equipment
  • Gas density monitoring in closed SF6 gas compartments
  • Remote monitoring of the SF6 condition
  • Raising an alarm when defined limit values have been reached

Special features

  • Ideally suited for smart grid or modernisation projects
  • Modbus® delivers measured values for pressure, temperature and gas density as digital signal
  • The 4 … 20 mA version outputs the absolute pressure at 20 °C [68 °F] or the gas density in g/l as an analogue signal for SF6 gas
  • Compact design with only one process connection
  • Suitable for alternative gases

Sales Contact (Wika.sales@asyatrafo.com)




Gas density is a crucial operating parameter for high-voltage plants. If the required gas density is not present, safe operation of the plant cannot be guaranteed.

The WIKA gas density measuring instruments provide reliable warnings against dangerously low gas levels, even under extreme ambient conditions. If the gas density drops as a result of a leakage, the switch contacts will switch. In addition to the traditional gas density monitor, with the model GDM-100-T high-precision sensors and evaluation electronics are incorporated.

Via the on-site display, the pressure based on 20 °C [68 °F] can be read directly on the instrument. With the integrated switch contacts, simple switching tasks can be realised quickly and without complication. The integrated 4 … 20 mA or Modbus® sensors integrated or attached to the instrument enable remote monitoring of the plant.

The measured data for pressure, temperature and gas density are transmitted using the standardised Modbus® RTU protocol. The model GDM-100-T can also be configured for alternative gases consisting of N2, CF4, O2, CO2, 3M™, Novec™ 4710, He and Ar.

The analogue version of the GDM-100-T uses the proven technology of the 4 … 20 mA analogue signal and outputs the absolute pressure at 20 °C [68 °F] or the gas density in g/l for SF6 gas as an analogue signal. The data storage enables trend analysis to be carried out, so that critical SF6 gas conditions can be predicted and rectified in time. An optimisation of the maintenance strategy from time-based (TBM) to condition-based (CBM) is possible through the use of the gas density monitor.

TBM =Time Based Maintenance
CBM= Condition Based Maintenance


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