4. Practical example: indirect measurement of relative humidity

In some cases, relative humidity cannot be measured directly. This is particularly the case where the measurement conditions do not physically allow the use of an impedance variation sensor, for example at high temperatures or in conditions close to saturation, conditions in which impedance variation hygrometers can suffer damage to the sensitive element.

In all cases, determining relative humidity using a condensation hygrometer in conjunction with a temperature sensor provides the lowest uncertainties on the calculated relative humidity value.

It's also important to bear in mind that vapor pressure diffuses very well in a climatic environment, and that it's sufficient to measure the dew point temperature at a single point in the test volume to be characterized, which is not the case with impedance hygrometers.

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