Service manual

Chapter 2 Principles
rejects the common-mode interference signal.
The low-pas filtering circuit filters the high-frequency interference signal beyond the frequency
band of the ECG signal.
The PACE signal refers to the ECG pace signal. It has significant interference to the ECG
signal detection. The PACE rejection circuit can rejects the PACE signal, which helps the ECG
signal detection.
The main amplifying/filtering circuit conducts the secondary amplification of the ECG signal,
filters the signal, and then sends the ECG signal to the A/D conversion part.
Pace Detect
This part detects the PACE signal from the ECG signal and sends it to CPU.
Temperature Detect Circuit
This circuit receives the signal from the temperature transducer, amplifies and filters it, and
then sends it to the A/D conversion part.
Carrier Generate Circuit
The RESP measurement is based on the impedance method. While a man is breathing, the
action of the breast leads to changes of the thoracic impedance, which modulates the
amplitude of the high-frequency carrier signal. Finally, the modulated signal is sent to the
measurement circuit. The purpose of this module is generating the high-frequency carrier.
RESP Signal Input Circuit
This circuit couples the RESP signal to the detecting circuit.
RESP Signal Process Circuit
The pre-amplifying circuit conducts the primary amplification of the RESP signal and filters it.
The detecting circuit detects the RESP wave that has been modulated on the actuating signal.
The level shifting circuit removes the DC component from the RESP signal.
The main amplifying/filtering circuit conducts the secondary amplification of the RESP signal,
filters the signal, and then sends it to the A/D conversion part.
A/D
The A/D conversion part converts the analog signal to the digital signal, and sends the signal
to CPU for further processing.
CPU System
 Implementing the logical control of all parameter parts and A/D conversion parts;
 Implementing the data processing for all parameters;
 Implementing the communication with the main board.
Power & Signal isolate Circuit
 Isolating the external circuits to ensure the safety of human body;
 Supplying power for all circuits;
 Implementing the isolation communication between the CPU System and the main board.
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