Erbe ICC 200, Service Manual

Page: 146 / 266

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3 CIRCUIT DESCRIPTION
The following assemblies are found on the PCB:
• Measured value acquisition and adjustment
• The contact monitor
• Actuation and power setting of the ST output stage
• Actuation of the power module
• Synchronization of the QK output stage
• Hardware electronic safety circuits
• Spark control
• Actuation of the QK output stage.
Measured value acquisition and adjustment
The measurement signals, which are triggered mainly to the Senso-board as well as to other parts of the
entire unit, move first to the control board where they usually must still be adjusted in order to finally move
on to the processor.
For most inputs, an input circuit consists of a variable voltage divider with which the signal voltages can be adjusted.
Various signal voltages, the values of which are needed very quickly by the processor system, proceed via
the amplifiers IC1 and IC2 directly to the processor. (See diagram page 2/3).
Other signals which are not required for fast processing can be fed to the processor system in multiplex
operation. (Circuit diagram page 3/3). These signals are fed to the 16-channel multiplex IC 3, scanned in
chronological order, then amplified in the operation amplifier IC1 and only then fed one after another to the
processor system (output ANALOG 4).
The individual operating voltages, for example, are determined in this way:
The +15 volt operating voltage is fed via the resistor divider R39, R40 to the multiplexer.
The +24 volt operating voltage is fed via the resistor divider R41, R42 to the multiplexer.
The –15 volt operating voltage is first fed via R31 to the operation amplifier IC2 by inverting it. Now the
voltage can also be processed as a positive parameter via the multiplexer which only switches through
positive signals.
The multiplexer IC3 receives its address actuation A0 to A3 from the control bus via the target memory (D-
flipflop) IC19.
The contact monitor
In the bipolar operating mode, it is necessary that the generator be switched on via the forceps when
biological tissue is found between the forceps tips. This is the purpose of the contact monitor. It should
switch on the generator at a tissue impedance of 2.5 kOhm.
In principle, two starting points can be specified and adjusted. The appropriate valid area is prescribed by
the control bus, stored in target memory IC20 and switched through there according to the activated output
(BER_1 or BER_2).
Control board
Slot J3