4.40 MOTHER BOARD RR-115 ID 5010-115
RIELE BERLIN Photometer 5010 / V4 4.40.10 22.09.2003
If selected temperature is reached it is switched over to a cooling level depending on the temperature:
• for 37 degrees Centigrade ⇒ cooling level 1
• for 30 degrees Centigrade ⇒ cooling level 2
• for 25 degrees Centigrade ⇒ cooling level 3
The cooling element is a Peltier element. The Peltier element functions as a heat pump and transports heat
out of the cuvette adaptor to the heat sink. The heat sink is provided with air by the fan of the device and
transports the heat outside to the area.
The Peltier element operates with a voltage, switchable on four levels:
• cooling level 0 ⇒ 0 VDC
• cooling level 1 ⇒ 0.5 VDC
• cooling level 2 ⇒ 1 VDC
• cooling level 3 ⇒ 1.65 VDC
Involved components are the microcontroller system IC3 (8031PLCC), the OP-booster IC1B (LM324), the
transistor T1 (BD679), the transistor T2 (BD243 with cooling body), the transistor T4 (BC547) and the Peltier
element.
Adjustment of temperature control
The voltage signal of the temperature sensor LM335 is at temperatures:
• 25 degrees Centigrade typical 2.98 V
DC
• 30 degrees Centigrade typical 3.03 V
DC
• 37 degrees Centigrade typical 3.1 V
DC
This means a change of 10 mVolt indicates of temperature change of one degree Centigrade.
Because of tolerances of the temperature sensor LM335 following can be measured at the measuring
amplifier:
• 25 degrees Centigrade ⇒ ≥ 2.92 V
DC
• 37 degrees Centigrade ⇒ ≤ 3.16 V
DC
The ADC converts the input voltage to a digital value between 0 and 32767 as shown on following diagram:
ADC
input voltage
of temperature sensor
32767
0
ca. 17000
ca. 13900
3,03 VDC
2,98 VDC
3,1 VDC
ca. 15200
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