English
In order to prevent condensation on piping, cooling ceilings, walls of equipment, etc., there are special resistive dewing probes used (Chap.11.4.1). By modifying the properties of a sensitive polymer layer they allow measuring high humidity. For this purpose, there are also conductive probes, which have two insulated electrodes on the mount, and the resistance between the two electrodes is measured (Chap.11.4.2).
The resistive probe with the polymer layer (Chap.11.4.1) can only be connected to the AI5 input of the C-AM-0600I module.
The probe with the isolated electrodes (Chap.11.4.3) can be attached to the AI5 input of the C-AM-0600I module, or to the inputs AI1 to AI3 of the modules C-HM-0308M, HM-C-1113M and C-HM-1121M.
In order for the dew sensor to function properly, it must have the same temperature as the surface that is to be protected against condensation, and access of air from the room must be provided. The sensor should be placed in the coldest point of the monitored ceiling or device; in water-cooled ceilings, the sensor should be installed on the cooling water supply pipes. The contact surfaces between the sensor and its seating can be coated with some thermally conductive paste. The exact procedure of placing the sensor in capillary ceiling cooling system must be resolved as per the ceiling cooling system manufacturer's instructions.
Pollution and aggressive chemicals affect the measurement accuracy and shorten the life of the sensor.
Dew point
What is usually specified is the temperature of the dew point. It is the temperature to which it would be necessary to cool the air (at a constant pressure), so that the water vapour contained in it becomes the so-called saturated steam. When the temperature is further reduced, the saturated steam is transformed into liquid and dew is formed.