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Microtherm Heat Stress WBGT

This product is now obsolete.

The Microtherm WBGT from Casella CEL is an ergonomically designed, compact, and rugged instrument designed to monitor heatstress potential of personnel in hot working environments in accordance with ISO 7243. It is the first heat stress meter that offers real-time graphical display of data and also features an audible/visual alarm which allows the operator to make rapid decisions if required. PC software for retrospective data analysis is included.

What is Heat Stress?

Workers exposed to hot working environments can be susceptible to heatstress, when the core body temperature rises to dangerous or hazardous levels. This can result in physiological symptoms like heatcramps, nausea, palpitations, stroke and possibly death.

An overall estimation of heat stress levels on the body can be measured by utilising the Wet Bulb Globe Temperature Index (WBGT). This combines the measurement of three parameters; natural wet bulb temperature (tnw), globe temperature (tg) and air temperature (ta), applied to the following formulae for both indoor and outdoor environments:

WBGT (Indoor) = 0.7tnw + 0.3tg

WBGT (Outdoor) = 0.7tnw+ 0.2tg + 0.1ta.

The data collected for these values are compared to reference values (as defined by the standard and appropriate "work rest" regimes) can then be adopted in the workplace or more detailed medical analysis undertaken. Key Features:

  Large LCD graphics display
  Real-time display
  Full data-logging facilities as standard
  Low water level warning
  Audible / visual alarm for WBGT levels
  %RH and dewpoint calculation
  Ergonomic design
  Long battery life
  10m extension cables available
  PC software included
  Meets requirements of ISO 7243
  Automatic calculation of work rest regimes via PC software
  Tripod mounting for meter and remote sensor array


  Power Stations
  Steel works
  Glass manufacturing
  Routine monitoring
  Medical surveillance testing


The WBGT meter measures simultaneously from three PRTD sensors for Wet Bulb, Dry Bulb and Globe Temperatures.

Sensors are manufactured to high accuracy standards:

BS EN60751 and DIN 43760.

Processed data values include:

  WBGT (indoor and outdoor)
  1 Hour (TWA) WBGT values
  Relative Humidity (%)

Sensors can be used either attached directly on the body of the unit, or remotely via 10m extension cables.

Both the electronic unit and sensor array can be tripod mounted (tripod not included).

Data Sheet


The Microtherm WBGT incorporates a large 128 x 64 pixel graphics LCD with backlight, capable of displaying data in two modes;

Graphical Representation

The Microtherm WBGT is the first area heat stress instrument to offer a real-time scrolling graph of the temperature parameters being measured. This display can be shown over variable time bases of 15, 30, 60 & 120 minutes. This allows the user to assess how the environment is changing over time, without having to download to a PC.

Numerical Values

Instantaneous values for all parameters are displayed, combined with the hourly rolling average values.


An adjustable alarm threshold may be defined for one selected data channel: WBGTtwa, WBGT, Ta or OFF. An audible alarm and flashing visual message on the display screen provides warning of excedence of the threshold.


Simple Keypad Operation

The Microtherm WBGT has been designed with a simple, easy to use menu structure for the displaying of information, instrument configuration and retrieval of data. The access of this menu via the touch keypad and screen prompts, ensures ease of use for the operator.


The software (WinHSM) provides an interface for data collection to PC for retrospective analysis. It produces graphical and tabular reports which can easily be imported into other applications. Summary and WBGT Heat Stress Index reports can also be generated. Work rest regimes are calculated, Clothing (Clo) correction factors, and metabolic rates can be entered in accordance with OSHA and ISO 7243.

Data can also be viewed "live" by selection of the real-time option whilst connected to the PC.


Calibration of the Microtherm WBGT is performed against an internal reference prior to every single measurement. This ensures a high accuracy for each of the temperature sensors and eliminates the need for annual recalibration. Sensor arrays are also interchangeable without need for recalibration.

Ordering Information

180000A - Microtherm Heat Stress WBGT meter with kit case
180042A - Microtherm Heat Stress WBGT meter with kit case with calibration certificate
180043B - 10m Extension Lead for sensor array
CEL-90330 - Small Tripod (max height 215mm)
CEL-6713 - Standard Tripod (max height 1,160mm)

Microtherm Heat Stress WBGT kit includes:

Microtherm Heat Stress WBGT meter
Sensor Array
Pack of spare wicks and screwdriver
Rechargeable batteries (x4)
Universal mains PSU (110/240VAC) with UK, Europe and USA plug adaptors
Distilled water countainer
RS232 communication cable (USB adaptor available)
Windows Win HSM software
Hard carrying case

Casella Measurement is now known just as Casella.

Please note - Product designs and specifications are subject to change without notice. The user is responsible for determining the suitability of this product.

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