Smiths Medical Medfusion 3000 Series, Техническое и сервисное руководство

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Theory of Operation
46
40-5648-51B
Plunger position sensing description
Sensing syringe plunger position is required for the
detection of an incorrect plunger speed, detecting near
end of plunger travel, and detecting end of plunger
travel.
The travel sensing circuits perform excitation and signal
processing of the travel sensor. The travel sensor uses a
linear potentiometer which produces a change in resis-
tance with the motion of the syringe plunger.
•
The sensing system requires calibration to deter-
mine offset and gain. Calibration values are stored in
non-volatile (serial EEPROM) memory.
Speaker drive description
The speaker sounds the warning and caution alarm
tones for the pump. The interface circuit controls the
frequency and amplitude of the signal driving the
speaker, and provides feedback for verifying speaker
function.
Speaker Amp
Envelope Control Circuit
A/D Channel 6
Amplitude Envelope Control
I/O Exp #1 PD0-PD2
Frequency, PW1
Volume, PW2
Speaker
Amplification
Speaker Test
Circuit
Illustration of Speaker Drive
Speaker control
• Tone duration is controlled by the interval the am -
plitude level is applied.
• The speaker_frequency signal is a fixed 50% duty
cycle (square wave) with a variable frequency to
1
kHz .
• The speaker_volume is a pulse-width modulated
signal converted by hardware to an analog voltage
which controls the speaker volume.
• The rise and fall times of the volume are controlled
by input signals from: speaker_envelope_1,
speaker_envelope2, and speaker_envelope_3.