Four decades of experience in gas density monitoring

A history overview of our long-term partner Trafag AG’s long experience in gas density monitoring.

The development of a temperature compensated pressure switch in 1978 marked the beginning of the era of Trafag’s density portfolio. An ingenious combination of a pressure switch with thermostat components made it possible to enter the density monitoring market of SF6 insulation gas in high-voltage switchgear. In 1987 Trafag developed the pioneering gas density monitor with reference gas chamber, a product with unsurpassed accuracy, vibration resistance and durability to this day. A metal bellows system plays the central role in this mechanical product. In 1994, Trafag bridged the gap of continuous gas density measurement and introduced the first electronic density sensor.


1978 Trafag introduces the first density monitor with pressure switches for the international market.

1987 Invention of the reference chamber principle that has become industry standard and introduction of density monitor type 87×0 with up to 3 microswitches.


1994 Invention of the oscillating quartz sensing element and introduction of the first electronic density sensor.

2003 Introduction of 8774 density sensor with current loop output. Later the portfolio was extended with 8775 type with digital RS485/ Modbus output.

2006 Introduction of density monitor type 87×6 with up to 4 microswitches. In the meantime, portfolio was extended with 87×8 type for use in arctic climate zones.


2008 Introduction of 90° (radial) process connection and the low-pressure indication dial.

2010 Introduction of the hybrid density monitor type 878x (current loop output) and 879x (RS484/Modbus output) that provides switchpoint monitoring and continuous density measurement in one device.


2014 Introduction of density monitor type 87×7 with up to 3 microswitches.

2017 Introduction of the integrated density monitor test valve.

2020 Introduction of the integrated insulating gas test and re-filling valve.

Originally published: Trafag