ZOLL M Series Defibrillator Rev R - Manual (Page 131)

M Series Service Manual
121
ECG Front End
The ECG front end provides an electrically isolated serial interface between the main system board functions and
patient interface ECG connectors. It performs the following:
• Analog ECG amplification and signal conditioning.
• Pacemaker pulse detection.
• ECG signals acquisition and analog to digital conversion.
• ECG 3/5/12-lead detection.
• ECG leads off detection.
• Front-end defibrillator protection.
• Isolated power conditioning.
• Patient impedance measurement via MFE or paddles.
Multifunction Electrode (MFE)/PADS (System Board and High
Voltage Module)
Selected for optimal performance for the application, a dedicated ECG amplifier with a limited bandwidth processes
the signal. It is then chopper modulated and coupled to the system side via an isolation transformer. On the system side,
the signal is synchronously demodulated, converted by a 10 bit A/D at 250 samples per second and digitally processed
by the main control unit of the system board.
To measure thoracic impedance, a high frequency (HF) measuring current passes through the patient’s chest and
measures the resulting voltage across the electrodes. After amplification, the impedance signal is synchronously
demodulated. It is then converted to a stream of pulses with frequency proportional to the measured impedance.
CPU and EPU
The Main System Board contains two microprocessors. A Motorola HC-11 single chip microprocessor is used to
acquire, convert and process ECG signals, (ECU). An Hitachi SH-3 RISC microprocessor acts as the system’s main
CPU. The SH-3 CPU and has an integrated on-chip multiplier, a cache memory, a memory management unit as well