January 2001
5F - 13
Functions - Cooling System
Service Manual Cafitesse 500
Temperature sensor (5)
●
The sensor is of the NTC-type. Its resistance
is reduced when the temperature rises.
●
The electronic control applies a constant
voltage to the sensor. The current which
depends in a linear way on the sensor
resistance is monitored by the electronic
control. This signal is used for the on/off
regulation of the Peltier current.
●
The "NTC" properties can be used to check
the cooling function. If both inputs of the
sensor on the electronic control are short
circuited the current to the Peltier element
must be on.
If the connection is unplugged the
electronic control must switch the cooling
system off.
Checking the sensor resistance:
●
Alternatively one of the two following
methods can be used:
a) Comparative measurement old - new,
at the same temperature
b) Resistance measurement and
comparison with the value from the
diagram. Due to self-heating the
measuring current must not exceed
1 mA.
Comparative measurement
Resistance measurement
Temperature sensor - resistance in Ohm
Temperature sensor - Temperature in °F
normal
normal
temp.
resistance
(°F)
(R) (Ohm)
14
27667
23
21156
32
16322
41
12690
50
9946
59
7851
68
6243
77
4998
86
4027
95
3265
104
2663
113
2185
0
5000
10000 15000 20000 25000 30000
0
°
F
20
°
F
40
°
F
60
°
F
80
°
F
100
°
F
120
°
F