Descriptions 10-5
Centrifuge 5804/5804 R and 5810/5810 R
10 Descriptions
Temperature monitoring (only refrigerated version)
Rotor chamber temperature
In order to measure the rotor chamber temperature, an NTC resistor is used which is encapsulated in a
sleeve and located on the rotor chamber base.
Depending on the temperature the sensor (NTC 10 k / 25 °C) changes its resistance. Via a voltage
divider (R8) this leads to a change of the voltage at the analogue input (PORT 7.0) of the processor.
Condenser temperature
In order to measure the condenser temperature, an NTC resistor is used which is fastened at the output
of the compressor.
This sensor (NTC 10 k / 25°C) serves as a protection against overtemperature. Via X11 and a voltage
divider (R7) it is connected to the analogue input of the processor PORT 7.1.
Locking mechanism of the lid
The locking mechanism consists of the lid motor drive, the lid position request and the position request
of the locking mechanism.
The necessary current is supplied to the lid motor by means of an IC driver (IC9). Depending on the
signal at the ports 4.2 and 4.3 the motor can rotate in left-hand or right-hand direction. Normally the
motor will rotate in left-hand direction when it opens as well as when it closes the lid. In case of a fault
(e.g. the locking bar is blocked) the motor will be rotated in right-hand direction after a certain time
(approx. 2 s) to loosen the blocking. For a short period of time (less than 1 s) during the locking process
it can draw up to 1.5 A current. This reduces the transformer voltage from 30 V to approx. 15 V.
The “ENABLE“ line, controlled by PORT 4.5, blocks the outputs of IC 9 when the locking mechanism for
the lid is inactive.
Two microswitches are used for the position request of the lid. They are located at the slots in the
housing in which the brackets of the lid are inserted. When these brackets are inserted into the slots
PORT 3.4 and 3.5 are connected to GND. In this way it is recognized that the lid is closed and can now
be locked.
In order to recognize the position of the locking mechanism the junction plate has one magnet each on
the upper and lower edge with opposite magnetic polarity. An analogue Hall sensor (SEN1) is located on
the control PCB which is influenced by these magnets. Without the influence of a field the voltage at the
sensor is approx. 2.5 V. When the lid is locked the lower magnet is positioned above the sensor and the
voltage is approx. 2.7 V. If the lid is unlocked the upper magnet is positioned above the sensor and the
voltage is approx. 2.3 V. Since this voltage can be measured at ANALOGPORT 7.3 it is possible to
request the position.
MSTM/KW/0408
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