ULTRATHERM 908i
28
gbo Medizintechnik AG 2004
Version 1.2
5.1.3.5. Subtracting amplifier
It includes: R212, R215, R214, N201/3, R256 up to the plug connector X211.
The difference of the voltages measured at X217 and X218 can be determined at X212, however,
the sign is changed.
5.1.3.6. Multiplier (N202)
The variable resistors R203 to R205 shall not be readjusted. They are provided for offset tuning of
the integrated circuit. At the output of the multiplier X216 a voltage U
0
must apply that can be
determined as follows:
U
Voltage at X
Voltage at X
0
215
214
10
=
•
(
) (
)
There shall be no voltage drop at the resistors R222 and R223. When after any integrated circuit
replacement a new offset tuning is necessary perform as follows:
•
0 V at U
in
•
Connect X214 and X215 to earth
⇒
set R205 to 0 V at X216.
•
Apply +5 V at X215, connect X214 to earth
⇒
set R204 to 0 V at X216.
•
Apply +5 V at X214, connect X215 to earth
⇒
set R203 to 0 V at X216.
•
Repeat the adjustment one times more. A 4.5 V flat battery can also be used instead of the +5
V.
5.1.3.7. Setpoint/actual value comparator
It includes: R221, R225, R226, C210, V214, N201/1.
A voltage, that is exactly proportional to the active output power delivered, applies at X216 where
2.5 V correspond to an output power of 250 W. By means of an suitable power meter the
adjustment is possible by R202.
In any case only one of the operational amplifiers N201/1 or N201/2 controls the voltage level.
The output at which the lowest voltage applies, pin 1 or pin 7, controls the level. In the case pin 1
controls, that means at pin 7 there applies about +14 V, only half of the voltage applying at X207
can be measured at X208.
With a good matching to X222 normally voltages of about +3 V to +9 V can be measured at pin 1
of N201/1 but the value depends on the RF power.
