Measuring Humidity
Ambient humidity :
Measurement unit : % rH (percentage of relative humidity)
Display : resolution to 0.5 % rH
Measuring range : from 2 % rH to 100 % rH
Measuring cycle : one measurement carried out every second
Precision : +/- 3.5 %
Response time: In the event of a sudden change in the humidity or temperature, one should
give the sensor enough time to allow it to adapt to the ambient air.
Please refer also to : Response time in the section "Measuring temperature".
Comments : In general, the following facts must be taken into account when measuring :
1. Ambient humidity depends on the temperature. When moving the instrument from a warm
environment to a cold environment, the values measured will vary ;
2. Humidity is not equally distributed in the atmosphere. Consequently, even though two locat-
ions used for measuring may be close to each other, both results may be quite different ;
3. A person perspiring and/or breathing very near the instrument may impact on
themeasurement.
Dew point :
The dew point is calculated by taking into account the humidity and the
ambient temperature. It gives the temperature at which the water vapour
contained in the air has reached saturation point (forming of cloud, fog, dew,
condensation on objects, etc.)
Example : At an ambient temperature of 23°C and with a humidity of
39.5 % rH, the dew point is at 12°C
(see Fig. 2)
Display : Press the temperature button for about one second, then release
it in order to display the temperature of the dew point.
The dew point in °C or °F is then shown in the lower part of the display, using the symbol .
Measuring Temperature
Ambient temperature :
Measurement units : In order to choose between units, press the temperature button
for approximately 4 seconds. The following selection will appear: °C (degrees Celsius) and
°F (degrees Fahrenheit).
Display : resolution to 0.5°C / 1°F
Measuring range : °C from -20 to 80 °F from -4 to 176
Measuring cycle : one measurement carried out every second
Fig. 2
