Pulsar
2
Service Manual
OPTIKON 2000
Cod. 111004SEN Rev.C
5-14
5.4 U/S DRIVER 347150
CONTROL
LOGIC
DIATHERMY
ADJUSTABLE
POWER SUPPLY
ULTRASOUND
The operating philosophy of the U/S Driver 347150 is shown by the block
diagram above.
The board contains both the U/S driver and the Diathermy driver, they share
the same adjustable power supply and they are both controlled by the same
microprocessor (NEC’s 78F0078).
5.4.1 SHEET 1/2
The U/S driver operates the piezoelectric handpiece, an electromechanical
resonating system, powered by a pair of piezoelectric ceramics that is kept
constantly tuned at its own oscillation frequency.
Ceramics are stressed by a sinusoidal voltage supplied by the u/s amplifier
section. At maximum power, this voltage features a peak amplitude equal to
500 V approx. with a frequency coinciding with the pilot signal supplied by the
Voltage Controlled Oscillator (VCO) section. Tuning accuracy is measured
reading the phase shift between the pilot signal (f) and the power signal (f’)
existing at the ceramic ends: the larger the phase difference, the better the
tuning.
This information is provided to microprocessor by the phase detector section,
that can provide the updated phase shift value at each new cycle of the pilot
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