2/Theory of Operation
2-20
1503-0151-000
3/27/97
Signals that are monitored by the ADC system include:
•
Flow DAC output
•
Flow Current sense
•
Inlet Valve Current sense
•
Patient Pressure
•
Manifold Pressure
•
Inspiratory Flow Sensor
•
Expiratory Flow Sensor
•
O
2
Concentration
•
Power Supplies
•
Battery Backup system
Multiplexer and Buffer Amplifier
The multiplexer settles quickly, within 8
µ
sec to 0.01%, to be stable for the ADC
12-Bit conversion and to maintain the overall 20
µ
sec conversion time. The sys-
tem bandwidth requirement is from dc to 20Hz. The multiplexer is an 8 channel
fault protected device and the amplifier used as a buffer to drive the A/D converter
(AD820AR).
A/D Converter
The MAX191BCWG is a 12-Bit converter that operates from a single 5 Volt power
supply. The clock frequency to run the A/D converter is 1.048MHz. It is derived
from the microprocessor system clock.
With a 1.048MHz clock, the conversion time of the A/D converter is 13 clock peri-
ods or 12.4
µ
sec, plus the 3
µ
sec required for the track/hold amplifier. The re-
sulting conversion time for the A/D converter is 15.4
µ
sec.
The MAX191BCWG has the following unadjusted dc accuracy specifications:
•
Integral Nonlinearity
±
1 LSB max
•
Differential Nonlinearity
±
1 LSB max (guaranteed monotonic)
•
Full-Scale Error
±
3 LSB max
•
Unipolar Offset Error
±
2 LSB max
Содержание Aestiva 7900 SmartVent
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Страница 18: ...1 Introduction 1 6 1503 0151 000 5 26 0 Notes ...
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Страница 158: ...8 Schematics 8 2 7900 Ventilator 1503 0151 000 1 97 Figure 8 1 System connection block diagram ...
Страница 159: ...8 Schematics 7900 Ventilator 1503 0151 000 1 97 8 3 Figure 8 2 SIB schematic diagram interface cable connections ...
Страница 160: ...8 Schematics 8 4 7900 Ventilator 1503 0151 000 1 97 Figure 8 3 Patient interface cable Machine side ...