GND
5 V
R
=
4, 27 k
Ω
ϑ
GND
SINP
SSUP
3-wire option for PT100
DRIVER
PLUG CABLE SENSOR
Figure 6.1:
schematic for connecting a temperature sensor
x
TCCK
:
0.2. . . 5
x
TCCN
:
5. . . 50
x
TCCV
:
0.2. . . 2
If you don’t know anything about the TEC circuit, you may set
x
TCCK = 0.2,
x
TCCN = 2
and
x
TCCV = 0.1. Then increase
x
TCCK slowly by 1 as long as the circuit stays stable.
When it becomes unstable, half the
x
TCCK value. Here the controller is operating
primarily as "P" proportional controller. After this try to find the value for
x
TCCN in the
same way. However, you may increase it by larger steps. At this point, the controller
behaves like a "PI" controller. Finally, you may increase
x
TCCV by steps of 0.3 until you
find an optimum value for response time and eliminate overshooting.
Note that you must stop and restart the temperature controller after changing those
values to make sure that the controller is initialized with the new values.
6.2 Temperature Sensor
The temperature sensor is connected over three pins of the laser & peltier interface:
GND, SINP and SSUP. The schematic in
shows the internal part of the driver
on the left hand side and a typical NTC thermistor connected to it on the right hand side. In
newer models, the SSUP and SINP are connected internally. Only the pins SINP and GND
are available externally.
The temperature is calculated by measuring the voltage using a voltage divider. After a
24 bit AD conversion the temperature
T
is calculated from the measured voltage
V
. For
this purpose the Steinhart-Hart equation is used by default.
T
(
R
NTC
) =
1
c
1
+
c
2
· ln
(
R
NTC
) +
c
3
·
(
ln
(
R
NTC
))
3
+
c
0
(
TSM1
)
24
