Shenzhen PM-9000 Express, Руководство по обслуживанию

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Chapter 2 Principles
2.2.4 SpO
2
Module
2.2.4.1 General
This module provides the function of measuring the Pulse Oxygen Saturation (SPO
2
).
2.2.4.2 Principle diagram
Figure2-7 Working principle of the SpO
2
module
2.2.4.3 Principle
The SpO
2
measurement principle
1. Collecting the light signal of the red light and infrared transmitting through the finger
or toe which is pulsing;
2. Processing the collected signal to get the measured result.
The drive circuit of the LED and the gain of the amplifying circuit should be controlled
according to the different perfusions and transmittances of the tested object.
Led Drive Circuit
This circuit supplies the LED with the drive current, which can be regulated.
SPO2 Signal Process Network
The pre-amplifying circuit converts the photoelectric signal to the voltage signal and conducts
the primary amplification.
The gain adjusting and amplifying circuit conducts the secondary signal amplification and
adjusts the gain.
The biasing circuit adjusts the dynamic range of the signal, and sends it to the A/D conversion
part.
A/D
The A/D conversion part converts the analog signal to the digital signal, and then sends it to
CPU for further processing.
D/A
The D/A conversion part converts the digital signal received from CPU to the analog signal,
and provides the control signal for the Led Drive Circuit and SPO2 Signal Process Network.
CPU System
12