159 / 2663 CIRCUIT DESCRIPTION
Art. No.: 80116-201
09 / 2004
Phase monitor for the patient circuit
The phase monitor determines the phase angle between the voltage and current in a high-frequency patient
circuit. In this way not only the apparent power, but also the active power emitted to the patient can be
calculated.
As already described in the current monitor and voltage monitor sections, the zero crossings of the voltage
and current characteristics are evaluated in the comparators of the open collector operation amplifier IC3
and summarized as “WIRED OR” in the load resistor R23. There is therefore a digital signal at the output
7 of the IC3, the pulse length of which corresponds to the phase relationship between the current and
voltage.
This signal is smoothed using the diodes D20 and D21, the resistor R40 and the capacitor C13 (averaging),
then amplified and decoupled via the operation amplifier IC9.
The voltage U_PHASE corresponding to the phase between the HF current and HF voltage is directed to
the control board and can be adjusted there using the trim potentiometer TP 7. The result is fed to the
processor.
The spark monitor for monitoring the spark cycle at the electrodes
During the cutting process, for example, there is sparking at the active electrode. To maintain a consistant
quality for the cut, the spark must be recorded and controlled in its intensity.
Our generators produce sine-wave output voltages with a very low distortion factor. If a spark occurs in a
patient circuit, harmonic frequencies of the output signal are thus produced by the nonlinear characteristic
of the spark channel. Harmonics can be either harmonics or DC voltage. This is why one can also say
“rectifier effect of the spark”.
The DC voltage resulting in this way moves from the patient circuit to the spark monitor of the ICC. It
moves via the resistors R1, R2, R4 and R5 to the Z-diodes D1 and D2, switched antiserially, which limit the
signal to 15 volts. Then follows the operation amplifier IC2, switched as an isolation amplifier, which
makes the DC voltage signal durable.
The DC voltage proportional to the spark intensity in the patient circuit must now be evaluated by the unit
and fed isolated to the unit circuit. The remainder of the circuit is in principle an isolation amplifier: DC
voltage signal is chopped, fed isolated via a transformer to the unit circuit and then rectified again.
The oscillator module IC1 produces a square-wave signal with a pulse duty factor of 1:1, present at outputs
10 and 11 of the IC1. This is the chopper frequency which actuates the transistor T1 and T2 in push-pull
operation. This push-pull amplifier functions on the output transformer UE5, which is operated via the
isolation amplifier IC1 using the spark voltage as the operating voltage.
In this way, the spark voltage is chopped from the transistors T1,T2 and fed via the transformer UE5 as an
isolation at the secondary side to the unit circuit as AC voltage.
Diode D15 then follows on the secondary side, which again rectifies the alternating signal thus resulting
and smoothes this by means of the capacitor C22.
Senso-board
Slot J7
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