V02 en, SCC_WE - 22 -
In order to measure the humidity inside the interior cabinet the following pysical principle is used:
When the fan wheel is turning, the rear fins create a differential pressure on pressure sensor p1 via the
connecting hoses (inner and outer connection).
The pressure sensor P1 is supplied with 12V DC. When the fan wheel is at a stand still, the offset volt-
age is between 0,45 - 0,55V DC.
The differential pressure is dependent on:
1. The speed of the fan wheel
2. The temperature in the cabinet
3. The amount of humidity in the cabinet
The following rules apply:
The output voltage of P1 is higher when the fan wheel turns faster.
The output voltage of P1 is higher when the cabinet temperature is lower.
The output voltage of P1 is higher when the humidity in the cabinet is lower.
This differential pressure is converted into a dc voltage for processing by the pcb.
Sample: SCC_WE 101E
NOTE: The given values are only average values and shall only demonstrate the relationship of pres-
sure values P1 to change in speed, temperature and humidity.
500 rpm 1000 rpm 1450 rpm 1550 rpm
Cold and dry 1,1V 2,2V 2,9V 3,1V
Warm and humid - Steam 100°C (212°F) 0,7V 1,7V 2,0V 2,2V
Hot and humid - Combination 180°C ( 0,6V 1,5V 1,7V 1,9V
Humidity control SCC_WE
Thermocouple B4
Humidity
Bus signal
Motor rpm
Differential pressure sensor P1
Humidity control
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