1.7 Connecting components
TED350 / page 12
The TEC element and the temperature sensor must be connected to the output jack
at the rear of the TED350 according to the shown pin assignment with shielded
cables.
The shielding of the cable must be connected to ground (pin 13,14,15).
1.7.2 Connecting a thermistor
The thermistor is set up between pin 3 and pin 4. The polarity is unimportant if the
thermistor is floating. If one pin of the thermistor is grounded (for example in a laser
module), this pin has to be connected to pin 3.
Using a thermistor, all temperatures are shown in ohms, therefore you have to look
for the corresponding temperature in the datasheet of the thermistor.
Figure 4
Connecting a thermistor
When the actual temperature "T
ACT
" is chosen for display the thermistor resistance is
shown. The pushbutton (F2, Figure 1) selects the resistance range of the thermistor.
In position "TH < 20 k
Ω
” the maximum thermistor range is 20 k
Ω
and the measure-
ment current 100
µ
A. In position "TH < 200 k
Ω
” the maximum thermistor resistance is
200 k
Ω
and the measurement current 10
µ
A.
The dependency of resistance on temperature and vice versa of an NTC-thermistor
is described by the formula:
val
val
T
T
B
B
R
R
T
T
B
R
T
e
R
T
R
val
+
=
⇔
∗
=
−
)
ln(
*
*
)
(
)
(
0
0
0
)
1
1
(
0
0
(temperatures in Kelvin)
