25/08/2004 ©
Söring
Service-Manual Arco- and RF-units
1
not valid for A-3000/ -2000
2
not valid for Arco-2000
-52-
3
not valid for MBC600
4
not valid for Arco-1000
11.3. Description of gas control board
11.3.1. General description of gas control board
The gas control board serves for control of the proportional valve and the magnetic
valves on the gas unit. Furthermore the signals of both pressure transducers and the
pressure switch are processed, digitally converted, and transferred to the CPU by a I
2
C-
bus.
11.3.2. Description of gas control board
Fig 11.2 shows the block diagram of the gas control board.
The signals of the pressure sensors and the pressure switch of the gas unit go through
the measuring amplifiers and signal conditioning to the I
2
C-bus interface. The electrical
feeding of the sensors is also done by the gas control board. A conversion of analogue to
digital measurement values is performed in the I
2
C-bus interface. These values are
transferred to the CPU for evaluation. The proportional valve as well as the magnetic
valves are controlled by the CPU via the bi-directional I
2
C-bus. A pulse width modulator,
controlled by the analogue to digital converter of the I
2
C-bus interface, feeds the
proportional valve with a rectangular signal of variable pulse width. This procedure
reduces hysteresis effects of the proportional valve, which otherwise could cause
oscillations during regulation. The power supply is ±15v.
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