Mindray PM-7000, Руководство по обслуживанию

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Chapter 2 Principles
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12-lead (8 channels): I, II, III, avR, avL, avF, V1-V6
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.
■
RESP
The PM-7000 measures the RESP based on the impedance principle. While a man is
breathing, the action of the breast leads to impedance changes between RL and LL.
Change the high-frequency signal passing the RL and LL to amplitude-modulation
high-frequency signal (AM high-frequency signal), which is converted to the electric signal
after being detected and amplified and then sent to the A/D converter. The RESP module
consists of the RESP circuit board and coupling transformer. The circuit has several
functions: vibration, coupling, wave-detection, primary amplification and high-gain
amplification.
2.4.3 NIBP
The NIBP is measured based on the pulse vibration principle. Inflate the cuff which is
on the forearm till the cuff pressure blocks the arterial blood, and then deflate the cuff
according to a specified algorithm. While the cuff pressure is decreasing, the arterial
blood has pulses, which are sensed by the pressure transducer in the cuff.
Consequently, the pressure transducer, connected with the windpipe of the cuff,
generates a pulsation signal. Then, the pulsation signal is filtered by a high-pass filter
(about 1Hz), amplified, converted to the digital signal by the A/D converter, and finally
processed by the MCU. After that, the systolic pressure, diastolic pressure and mean