ATEX Transmitters For Hazardous Area Temperature & Humidity Measurement From Rotronic

Published 25 Sep 2016


Temperature & Humidity Measurement




ATEX Transmitters

Rotronic HygroFlex5-EX – ATEX Transmitters For Temperature & Humidity Measurement In Potentially Explosive & Hazardous Area Locations

  • By Chris Dodds : estimated reading time 8 minutes

Thanks to David Wyshnia (Area Manager, Rotronic Instruments Ltd) for this Guest Blog about the need for hazardous area certified ATEX transmitters, including the Rotronic HygroFlex5-EX in potentially explosive environments.



The oil and gas industries are obvious examples of where potentially explosive environments exist, but other industries have their own set of hazardous area conditions that need to be monitored and controlled using ATEX transmitters – suitably certificated temperature and humidity measurement sensors.

Fine particulates from sugar beet processing, wood dust, pharmaceutical powders and vapours from paint spraying processes are also examples of where equipment, including products designed and manufactured for “own” use, are not excluded from the requirements of the ATEX Directive.

In the Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR) an explosive atmosphere is defined as a mixture of dangerous substances with air, under atmospheric conditions, in the form of gases, vapours, mist or dust in which, after ignition has occurred, combustion spreads to the entire not burnt mixture.Dangerous Substances and Explosive Atmospheres Regulations 2002 (DSEAR)

Atmospheric conditions are commonly referred to as ambient temperatures and pressures.

That is to say temperatures of –20°C to 40°C and pressures of 0.8 to 1.1 bar.

The Swiss based company, Rotronic Instruments, have been manufacturing and supplying ATEX transmitters for hazardous area measurement of temperature and humidity levels for over 20 years.

The accuracy, durability and the reluctance of their probes to drift are seen as key attributes for companies who work in challenging conditions.

Rotronic’s new HygroFlex5-EX range of Wall and Duct mounted transmitters comply with all the current ATEX regulations. They have greatly simplified the installation and maintenance of ATEX equipment with galvanic separation and no need for an intrinsically safe power supply.  Their “Hot Swap” probes also significantly reduce line downtime when probes require calibration, enabling the user to attach a replacement sensor in seconds without having to unwire / rewire the transmitter.

ATEX Transmitter

Hazardous Area Classification.

ATEX EX II 2(1) G Ex eb mb [ia Ga] IIC T5 Gb

ATEX EX II 2(1) D Ex tb [ia Da] IIIC T80°C Db

Atex transmitters

Hazardous Area EX Certification – North America

  • Class I, Div 1/2, Groups ABCD T5…T4,
    Class II, Div 1/2, Groups EFG T80°C…T110°C
    Ex e mb [ia Ga] IIC T5…T4 Ga/Gb
    Ex tb [ia Da] IIIC T80°C…T110°C Da/Db
    Class I, Zone 0/1, AEx e mb [ia Ga] IIC T5…T4 Ga/Gb
    Class II, Zone 20/21, AEx tb [ia Da] IIIC T80°C…T110°C Da/Db

All probes have a working range of -40°C…+85°C / 0…100 %rh. The aluminium housing of the transmitter (with display) -10°C…+60°C.

Humidity & Temperature Measurement

In Dust Hazard Zones 20, 21, 22

ATEX transmitters are certified for safe use in hazardous area industries affected by potentially explosive atmospheres – typical dust hazards include:

  • Food Dust – colourings, chocolate, milk, flour, sugar, starch, cereal
  • Plant Dust – wood, bark, cork cotton, paper
  • Metal Dust – aluminium, magnesium, ferro alloys

Additional dust hazards from industrial processing include plastics, powder coatings, fertilisers, rubbers, elastomers, resins and synthetic adhesives – if in doubt about the specification or purchase of hazardous area transmitters or electrical products please contact T&D, we are Experts In Explosive Atmospheres.

Electrical Equipment For Hazardous Area Explosive Gas Atmospheres
IEC Standard EN Standard Contents
IEC 60079-0 EN 60079-0 General requirements for equipment for use in explosive atmospheres with the presence of gas and dust
IEC 60079-31 EN 60079-31 Explosion Protection by enclosures “t”
IEC 60079-2 EN 60079-2 Explosion Protection by pressurization “p”
IEC 60079-11 EN 60079-11 Explosion Protection by intrinsic safety “i”
IEC 60079-18 EN 60079-18 Explosion Protection by encapsulation “m”


Choice of SENSING Probes

There are a range of Rotronic probes available for the HygroFlex5-EX series to meet specific applications. Apart from the standard probe there are also cable probes with 2/5/10 metre cable lengths.

HC2-IM-EX Humidity & Temperature Probe

HC2-IM-EX Humidity & Temperature Probe

For processes that require humidity and temperature measurements under pressure the Rotronic HC2-IE-EX probe may be employed. Available with either ½”G or ½” NPT thread and with cable lengths of 2/5/10m the probe is pressure resistant to 100 bar / 1450 PSI.

HC2-IE-EX Humidity & Temperature Probe

HC2-IE-EX Humidity & Temperature Probe





Low Dew Point

To measure trace moisture in bodies such as gas pipes or compressed air systems the Rotronic HC2-LDP-EX provides highly accurate dew point and temperature measurement up to 100 bar.

HC2-LDP-EX Dew Point & Temperature Probe

HC2-LDP-EX Dew Point & Temperature Probe









Diagramatic layout for various hazardous area Zone applications

Diagramatic Layout for Various Hazardous Area Zone Applications

Transmitters & Sensors – Zone 1, Zone 2 Zone 21 & Zone 22 Certified According To Hazardous Area ATEX Directive.

Islands of Self Sufficiency

Layered on top of the DSEAR regulations are a company’s individual practices and processes which determine how often process instrumentation needs to be calibrated.

In order to be self-sufficient, whether from a geographical or process driven perspective, many companies have also taken on board the Rotronic HygroGen2 humidity and temperature generator. The HygroGen2 sets a new standard in terms of portable calibration.

The generator is not exclusively for use with Rotronic probes. Many different manufacturers’ instruments can be calibrated by use of interchangeable diameter port sleeves, clear acrylic and even custom made doors. The user simply enters the required temperature and humidity set points to build a calibration profile.

The range of the Rotronic Hygrogen2 is:

0….60°C (-5….60°C with optional range extension)
5….95 %rh (2….99 %rh with optional range extension)

Temperature control stability at equilibrium is better than ± 0.02 °C whilst humidity control stability is better than 0.1 %RH. Full details are available on the Data Sheet.

Rotronic HygroGen2

Rotronic HygroGen2 – Calibration of temperature and humidity instrumentation.


One of the main benefits of the Rotronic HygroGen2, when used in conjunction with Rotronic’s HC2 series probes, is the ability to automatically calibrate the probes (and adjust if required). The AutoCal feature also creates a PDF calibration certificate for each probe under test.

20 storable programmes each with 200 set points provide the flexibility to quickly recall standard profiles for efficient use. Humidity equilibrium between set points is typically achieved in around 5 minutes – a considerable time saving when compared to using calibration salts.

“The installation of the Rotronic ATEX transmitters on a blending suite was simple and the hot swap probes will virtually eliminate line downtime. The calibration of the probes is now so quick that we even adjusted them out, and back in, just to see how it would work and found the adjustments very logical and easy to complete. For us, these new probes along with the HydroGen2 chamber represent a huge step forward in the calibration of temperature and humidity instrumentation”Dave Gregson, GlaxoSmithKline

HygroGen2 with AutoCal Function

HygroGen2 with AutoCal Function

Reducing Uncertainty in uncertain environments

At the very highest level of measurement such as National Standards Laboratories, MBW chilled mirror hygrometers are considered to be the most accurate, reliable and consistent humidity measurement technology available. They are a primary reference standard against which other sensors are calibrated.

As well as calibration laboratories, MBW chilled mirrors are used in oil and gas applications, chemistry laboratories and throughout meteorological, processing, manufacturing, engineering and storage industries across a dew/frost point range of -95°Cfp to +95°Cdp and pressures up to 200 bar.

Rotronic has worked closely with MBW, to integrate their products into the HygroGen2 portable temperature and humidity calibration system. Particularly well suited is the MBW 473 Dew Point Mirror, whose RP2 measuring head is designed to be directly inserted into the working volume of the Rotronic HygroGen2 chamber and work across its full range. Temperature and humidity probes from all manufacturers can be calibrated with typical expanded measurement uncertainty at ambient conditions of less than 0.7 %rh


More Rotronic Reading

 ➡ ATEX Certified Humidity & Temperature Sensors – Rotronic HygroFlex5-EX

 ➡ How Much Does It Cost If Your Production Capabilities Are Down For An Hour? 

 ➡ Rotronic HygroClip – Relative Humidity & Temperature Measurement Module Explained

Rotronic HygroFlex5-EX - Hazardous Area Temperature Measurement ATEX Zone 1

Rotronic HygroFlex5-EX – Hazardous Area Temperature Measurement ATEX Zone 1.

Invitation – network, engage, promote

Thorne & Derrick are inviting you to join LinkedIn’s fastest growing Discussion Group – Process & Hazardous Area Industries : Heat Tracing, Gas Detection, Fluid Control & Flow Measurement. News, projects, videos, promotions, whitepapers, jobs, webinars, press plus much more. Instrumentation, Mechanical, Heating, Metering, Process, Flow Control - Hazardous Areas

Further Reading