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2.4.2 ECG/RESP
ECG
The DPM4 patient monitor has the following ECG functions:
1. Lead type: 3-lead, 5-lead, 12-lead
2. Lead way:
3-lead (1 channel):
5-lead (2 channels):
12-lead (8 channels):
I, II, III
I, II, III, aVR, aVL, aVF, V
I, II, III, aVR, aVL, aVF, V1-V6, CAL
3. Floating input
4. Right-foot drive
5. Lead-off detection
6 2-channel ECG waveform amplification; processing ECG signals of any two leads
The ECG circuit processes the ECG signals. It consists of the following parts:
1. Input circuit: The input circuit protects the ECG input level, and filters the ECG signals
and external interference. The ECG electrode is connected to the input circuit through the
cable.
2. Buffer amplifying circuit: This circuit ensures extremely high input impedance and low
output resistance for ECG.
3. Right-foot drive circuit: The output midpoint of the buffer amplifying circuit is fed to
the RL end of the 5-lead after the inverse amplification, so as to ensure that the human body
is in the equipotential state, decrease the interference, and increase the common-mode
rejection ratio of the circuit.
4. Lead-off detection: The lead-off causes changes in the output level of the buffer
amplifying circuit. Therefore, the lead-off can be detected with a comparator, and the state
of lead-off can be converted TTL level for the Micro Controller Unit (MCU) to detect it.
5. Lead circuit: Under the control of MCU, the lead electrodes should be connected to the
main amplification circuit.
6. Main amplification circuit: The measurement amplifier is composed of 3 standard
operation amplifiers.
7. Subsequent processing circuit: This circuit couples the ECG signals, remotely controls
the gains, filters the waves, shifts the level, amplifies the signal to the specified amplitude,
and sends the signal to the A/D converter.
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