Gymna Pulson 330, Service Manual, Page: 25 / 49

When the instrument is switched on, the relays is not
activated. At this time the
µ
p has the possibility to detect the head
size of the head connected to CON2.
After a second, the relays will be activated and head size
detection of CON1 is performed.
However, only the 3MHz head has a head detection bridge inside
the plug. This means that the
µ
p at this point is unable to see if
either there is a 1MHz head connected, or there is no head
connected. Therefore the RPOT lines are used.
Since all heads do have a resistance fixed in the plug, the
µ
p
can always see whether a head is connected or not.
In other words, by checking the head sizes of both outputs (by
means of RLY3), and by taking the RPOT values into consideration, the
µ
p knows which heads are connected to which outputs.
After detection, the relays will choose the 1 or 3MHz output of
the harmonic filters. At this point, the position of the
relay at the head size detection is of no importance.
The relay, and its led, will be activated in case of the 1MHz
selection.
13.3 Contact control
order to detect the quality of contact between the ultrasound head
surface and the treated tissue, the equipment processes the measured
voltage and the measured current through the ultrasound head.
If the equipment decides that there is something wrong, USH may be
displayed ( see error codes page 23 ).
If the equipment detects a ‘bad contact’ situation, the intensity
,which was last measured, blinks on the intensity display. The output
power is reduced and a control led, installed on the head, will light
up.
As soon as The contact is sufficient, the intensity stops blinking
and the microprocessor directs the AD converter ( U15 ) in a way that
it gives the same output voltage as there was before the bad contact
situation, which should result in the same US power output as before.
However, when the contact between the treatment head and the patient
is not as good as before, there can be a slight difference.
In other words, when the power before bad contact was e.g. 1.7 W/cm²,
it is possible that in the end it results in an output power of 1.5
W/cm².
In case of insufficient contact the CONTACT output will be logic high,
Q4 opens and a DC voltage is fed to the led in the ultrasound head.
L5 and C89 filter out reverse HF noise, which may possibly disturb
the
µ
p.
13.4 Cable fraction detection.
The Pulson 330 is provided with a detector, which constantly monitors
the cable of the active US head.
In case of a cable fraction, the display shows Cab, and the treatment
is ended.
( See output stage schematics)
When the contact of the US head is sufficient, the led on the head
will extinguish.
The microprocessor now starts to give a short pulse on the led.
In fact, this pulse is short enough, so the human eye cannot see it.
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