ZOLL E Series Monitor Defibrillator Rev D - Manual (Page 102)

E Series Service Manual
4-6 9650-1450-01 Rev. D
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). A Hitachi SH-3 RISC microprocessor acts as the system’s main CPU. The SH-3 CPU has an integrated on-chip multiplier, a cache
memory, a memory management unit as well as data protection and virtual memory functions. It also has a timer, a real time clock, an interrupt controller,
a serial communication interface (SCI), and other peripheral functions necessary for the system operation. The memory circuitry includes Flash ROM,
internal flash non-volatile memory and DRAM.
The EPU acquires ECG data and runs the A/D convertor that sends data in the form of a serial stream to the CPU.