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Thermohygrometer BC25
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  5. BC25 thermohygrometer

BC25 thermohygrometer

Climate measurements including 'heat index' and 'apparent temperature'

Precise climate meter in pocket format

The BC25 is a both effective and handy instrument for reliably determining a measure for the physical stress resulting from high temperatures in combination with high humidity levels. For a high humidity level affects the thermal regulation of the body by evaporation of sweat. This way, the subjective well-being is considerably impaired and the risk of a heat stroke is objectively increased, particularly for sportsmen as well as sick and elderly people.

With its sensitive sensor system, the BC25 therefore not only determines common climate parameters such as the air temperature, relative humidity, dew point and wet-bulb temperature, but also the 'heat index' (HI) and the 'apparent temperature' (WBGT index). Both the heat index and the so-called wet-bulb globe temperature provide information on the apparent temperature based on the measured air temperature and in particular the relative humidity and other parameters such as the heat radiation.

Due to the alarm functions of the BC25 for heat index and apparent temperature, thermal damage can be avoided from the start and the limits of stress resistance at high temperatures can be set. The large and easily readable LCD display as well as the functions for automatic switch-off, minimum and maximum value, AVG and HOLD complete the range of features of this innovative measuring device.

A good indicator of your well-being.
What does the heat index (HI) indicate?

The heat index, also referred to as humidex, is an indicator developed in the 1970s by the American Steadman. It describes the combined effect of temperature and (high) humidity levels on the human body.

The higher the relative humidity, the worse or slower does the moisture (perspiration) emitted by the human body evaporate as the ambient air can only absorb little additional moisture. This evaporation, however, is necessary for the human organism to be able to regulate itself in case of strong heat or physical exertion and to keep the core body temperature on a healthy level. If this natural cooling mechanism is slowed down, the body can no longer discharge the generated heat properly, which results in so-called heat stress. Overheating or heat strokes can be among the health consequences.

Even without any physical effort, high temperatures combined with high humidity levels (muggy heat) are therefore generally considered as unpleasant, while high temperatures and low humidity values are more tolerable.

Sweating and the associated cooling effect are thus vitally important for both humans and many mammals, and are indispensable for the physical well-being.

The international standard for the climate influence on the human body: wet-bulb globe temperature index (WBGT index)

The wet-bulb globe temperature index is a climate index developed by the US army as early as in the 1950s. It serves to specify the effects of the current climate on the human body.

Unlike the heat index, the WBGT does not only incorporate the air temperature (dry-bulb temperature) and humidity level, but also the wind speed, the wet-bulb and radiation temperature (globe temperature) for assessing the outdoor thermal stress.

The wet-bulb temperature (or theoretical limit of cooling) is the lowest temperature that can be reached through direct evaporative cooling only. It is determined by wrapping a cotton cloth soaked with distilled water around the measuring tip or mercury bulb of a thermometer and then exposing it to the environment. The cooling effect achieved by the evaporated water can thus be measured and simulated for the perspiring human body under these conditions.

The radiation temperature, which is also taken into consideration, is measured inside a thin-walled matt black globe reacting to the infrared heat radiation emitted by the sun. Therefore, the WBGT index is another indicator for determining the climate effects on the human organism. It is, however, even more informative than the heat index since additional parameters are included in the calculation. Established as an international standard, it is described in ISO 7243 and DIN EN 27243.

Special features of the BC25

BC25 - Dimension
Handy and always with you: the compact BC25 thermohygrometer fits in any jacket or trouser pocket.
BC25 - WBGT Index
The heat index and the WBGT index provide information on whether physical exertion is advisable in the prevailing climate conditions.
BC25 - Heat index
The heat index and the WBGT index provide information on whether physical exertion is advisable in the prevailing climate conditions.
BC25 - 6 functions
Functional diversity: The BC25 displays the temperature, relative humidity, dew point temperature, wet bulb temperature and WBGT or heat index.
BC25 - Battery operated
The BC25 hand-held meter is operated with a 3V button cell battery.

Application examples from practice:

BC25 - Climate measurement during sport
It's hot and muggy. Check whether the climate conditions are beneficial for your sporting activities.
BC25 - Climate measurement for old or sick people
Elderly or sick people have to take special care in order not to overstrain themselves on hot days.
Technical data by comparison

All climate measuring devices in direct comparison:

To find the climate measuring device which exactly meets your requirements, please consult the concise overview of all climate measuring devices from Trotec, which we're providing to you here so that you can compare them directly to each other.

Models which you do not wish to include in your comparison can be easily dismissed with only one click.

Technical data by comparison

A few practical benefits:

  • Determination of climate parameters °C/°F, %RH, dew point, wet-bulb temperature, heat index (HI), apparent temperature (WBGT)
  • Alarm function for heat index (HI) and apparent temperature (WBGT)
  • Large and easy-to-read LCD display
  • Automatic switch-off
  • Max/Min/AVG function
  • Hold function
  • Optimum value-for-money ratio


Thermohygrometer BC25 inkl. Hitze-Index (HI) und gefühlter Temperatur (WBGT) Anzeige show in Trotec online shop

Technical data

Technical data
General information
  Article number 3.510.205.008
Air temperature [°C]
  Min. measuring range | Air temperature [°C] -20
  Max. measuring range | Air temperature [°C] 50
  Resolution [°C] 0.1
  Accuracy ± -20 °C - 50 °C [°C] 0.6
Air temperature [°F]
  Min. measuring range | Air temperature [°F] -4
  Max. measuring range | Air temperature [°F] 122
  Resolution [°F] 0.1
Relative humidity (%)
  Min. measuring range | Relative humidity [%] 0
  Max. measuring range | Relative humidity [%] 99.9
  Resolution | Relative humidity [%] 0.1
  Accuracy 10 % - 90 % [%] 3
  Accuracy 0 % - 10 % [%] 5
  Accuracy 90 % - 99.9 % [%] 5
Device control
  Push buttons
Housing design
Power supply
  Internal (battery) 1 x 3 V, CR2032
  Length (packaging excluded) [mm] 142
  Width (packaging excluded) [mm] 20
  Height (packaging excluded) [mm] 36
  Length (packaging included) [mm] 170
  Width (packaging included) [mm] 37
  Height (packaging included) [mm] 64
  (packaging excluded) - batteries included [kg] 0.052
  (packaging included) [kg] 0.097
Standard scope of delivery
Standard scope of delivery
  Measuring device
  Operating manual
Ascertainable measured values and functions
Functions and features
  Heat index (HI)
  Apparent temperature (WBGT)
  Wet-bulb temperature
  Switching function °C/°F
  Minimum value display
  Maximum value display
  Average value display
  Measured value hold function
  Alarm function for heat index (HI)
  Alarm function for and apparent temperature (WBGT)
  Automatic switch-off

 standard equipment

 optionally available

 not available



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