Vaisala DM500 - Manual (Page 29)

Chapter 4 _________________________________ General Information About Sampling and Results
VAISALA _______________________________________________________________________ 27
The Effect of the Ambient Temperature on
Cooling Capacity
The cooling capacity of the sensor is dependent on the cooling air
temperature, as shown in Figure 7. In general, the cooler the ambient
air is, the lower dewpoint can be reached. By using air as a cooling
medium, the lowest normally achievable dewpoint is about -50 ºC.
When measuring lower dewpoint, water cooling must be used.
Recommended air temperature: 10...40 ºC (50...104 ºF), depending on
the measured dewpoint.
Water cooling is recommended when measuring dewpoints > +40 ºC
(+104 ºF).
Figure 7 Effect of Ambient Air Temperature on Lowest
Achievable Stable Sensor Temperature