Maquet Servo ventilator 900 C, Руководство по обслуживанию

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27
= Not valid for SV 900 E
= Not valid for SV 900 D
Direction & speed selection
(PC board no 6)
This is a multiplexer and the output signals are direc tion
and speed. The output signals come from the VOLTAGE
CONTROLLED OSCILLATOR during normal operation,
from FAST OPENING OSCILLATOR during beginning of
INSP. TIME in all PRESSURE REG. CONDITIONS except
PRESS. CONTR. mode, and from POWER OFF OPENING
OSCILLATOR when mains is switched off or at power
failure.
Fast opening oscillator (PC board no 6)
This oscillator is set (R37) to a frequency corre sponding to
a step motor speed of approximately 480 steps/second.
Fast opening control (PC board no 6)
This stage will initiate a fast opening of the inspira tory
valve at the beginning of each PRESSURE REG. INSP.,
except during PRESS. CONTR. mode. This condition will
be kept up until the INSP. FLOW exceeds 0.17 l/second.
Power off voltage (PC board no 6)
This stage delivers stored energy to control the ope ning
of the inspiratory valve (step motor) when the mains is
switched off.
Power off opening oscillator
(PC board no 6)
The freqency of this oscillator is selected (R92) within
250-400 Hz.
Electronic unit – Regulation of inspiration
End position protector (PC board no 6)
The purpose of the END POSITION PROTECTOR (V27) is
to stop the VOLTAGE CONTROLLED OSCILLATOR when
the step motor is at either of the two end positions and
the direction signal indicates that the motor should step
beyond these positions.
The VOLTAGE CONTROLLED OSCILLATOR is
blocked if one of the following conditions is fulfilled:
•
The inspiratory valve is fully open and the direc tion
signal indicates additional opening.
•
The inspiratory valve is fully closed and the direc tion
signal indicates additional closing.
• The inspiratory valve is fully closed and the in spiration
time signal is low.
Step motor driver (PC board no 6)
The STEP MOTOR DRIVER is an up-down counter
(consisting of C-MOS circuits V22 and V23 and an
output buffer stage V24). The driver stage receives speed
information (the pulse frequency) and direction information
(forward or backward) via DIRECTION AND SPEED
SELECTION block. The driver stage has 8 outputs, two
for each motor winding. The windings are activated in a
specific sequence, so that the step motor will move an
angle of rotation of 3.75° at each step (positioning).