Erbe ICC 200, Service Manual

Page: 158 / 266

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3 CIRCUIT DESCRIPTION
The following assemblies are located on the PCB:
• Current monitor for the patient circuit
• Voltage monitor for the patient circuit
• Phase monitor for the patient circuit
• Spark monitor for monitoring the sparking at the electrodes
• Safety system for the neutral electrode (NESSY)
• Relay control
Current monitor for the patient circuit
The high-frequency current moves from the generator to the Senso-board via the connectors J1 and J2. On
the way to the electrodes, the current is directed by the transformer UE1, the load resistors R11 and R12 of
which are transformed at a ratio of 2500:1 to the primary side and thus serve as a shunt for current
measurement.
The output voltage of the secondary winding is also proportionate to the high-frequency output current.
This voltage now moves to one of the operation amplifiers IC7 and IC8, which represent an »ideal rectifier«
together with the diodes D27, the capacitor C30 feedback resistor R30.
The rectified voltage IP_PAT is lead via the control board to the processor and, after further amplification
in the operation amplifier IC8, is also lead as voltage IP_PAT A for adjustment at the trim potentiometer
TP6 also to the processor.
The output voltage of the transformer UE1, on the other hand, moves after a restriction through the diodes
D16, D17 to the comparator IC3, the open collector of which operates at the resistor R23. There the zero
crossings of the HF current are detected, together with the second part of the comparator IC3, at the output
of which a signal according to the zero crossing of the HF voltage is present. Using the common load
resistor R23, this circuit represents a “WIRED OR”. There is a digital signal at the output the pulse length
of which corresponds to the phase relationship between voltage and current of the HF signal.
The voltage monitor for the patient circuit
Parallel to the lines which lead to the active electrode AE and the neutral electrode NE, the high-frequency
voltage is picked up and led via the capacitor C1 to the transformer UE2, which transforms the voltage by
a factor of 12.5 weakened to the secondary winding.
After a further halving of the measurement voltage in the resistor divider R15, R16, it moves, similar to the
situation in a current monitor, to an active, ideal rectifier, consisting of the operation amplifiers IC4, IC8 as
well as the diode D23, the capacitor C33 and the negative feedback resistor R52. The parameter for the
high-frequency patient voltage UP_HF is then led to the processor via the control board, as is also the
amplified signal UP_HF A.
At the same time, the output voltage of the transformer UE2 is directed to the comparator IC3 which emits
a digital signal to the “WIRED OR” during its positive phase. (See above for description).
Senso-board
Slot J7