5.4.4 Impedance matching
The ultrasound crystal is mainly a capacitive load. Its impedance differs, among other things, with
the size of the crystal and its operating frequency. For this reason the micro controller can match the
impedance by switching one or two inductors and when necessary capacitors in the output stage.
5.5 RS 232 communication.
This interface is used for:
• externally programming the device (service)
• internally programming the device (production)
• future applications
The signals that are used for sending and receiving data from and to an external device, must be
isolated according to IEC601. Also the supply must be isolated.
The supply is isolated via a transformer and the signals are isolated with opto-couplers.
At both sides of the opto-couplers a send/receive IC is necessary to comply to the standard levels.
The maximum speed of the connection is mainly determined by the speed of the opto-couplers which
is 38400 bits/sec (baud rate).
Downloading new software will take approximately 10 minutes.
5.6 Vacuum unit.
5.6.1 General information.
The Guidance E/C has a 2 channel integrated vacuum module with the following specifications:
Continuous mode: 50 Æ 320 mBar +/- 10% on maximum level.
Pulsed mode : 65Æ 480 mBar +/- 10% on maximum level.
Rhytm on/off time (sec): 1.5/6.0 ; 1.5/4.5 ; 1.5/3.0 ; 1.5/1.5
The vacuum module has the following components:
- Water reservoir.
- Pump.
- Rhythm valve.
- Valve channel A.
- Valve channel B.
- Vacuum PCB.
Since the electrotherapy channels work completely independent, it also goes for the vacuum channel.
This means that the therapist is able to work eg. on channel A with electrodes and on Channel B with
vacuum.
Switching on/off the vacuum can be done by means of a parameter selection on the therapy menu.
The vacuum pressure for both the channels must be set by means of the vacuum knob on the front
side of the unit.
Phyaction Guidance E/C – service manual version 0.5 Page 22
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