Mindray Passport 5-Lead, Руководство по обслуживанию

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Block Diagrams Theory of Operation
2 - 10 0070-00-0420 Passport 5-Lead, 5L, LT, XG Service Manual
2.2.2 Frontend Board/Daughter Board
Overview
The Passport Frontend Module consists of nine major blocks: the ECG, pressure, respiration,
temperature, isolated power supply, A/D converter, isolated microcontrollers, non-isolated
microcontroller, and data isolation sub-systems.
The ECG channel has five lead capability. It has an analog gain of 390, incorporates pacer
detect/reject processing, and electrosurgery interference detection function.
The dual invasive pressure channels each provide for a linear input range of -20 to +300
mmHg and can reject up to 120 mmHg of offset. The P1 channel systolic trigger level is fixed
at approximately 18 mmHg.
Patient respiration monitoring is accomplished using standard impedance pneumography,
actively driving a patient through the RA and LA ECG leads with several hundred
microamperes at 114kHz. Respiration can be measured over a range of 50 to 2000 ohms
equivalent body impedance. The circuitry outputs a signal representing a modulation of this
impedance, up to a maximum of 10 ohms.
The temperature preamplifier is capable of measuring with either 400 or 700 series
thermistor sensors. Measurement is valid over the range of 15 to 45 degrees C. Integral
calibration is provided internally at an equivalent temperature of 37.5 degrees C.
The Frontend Module creates its own isolated power from the system’s bulk power source,
which is either an unregulated 11 to 18 volt supply, or a battery supply of 11 to 14 volts. The
power conversion is implemented with a switch mode forward converter, to provide an
isolated supply of approximately 8 volts. Reg5 volts for circuitry and pressure
transducers is accomplished using series linear regulators.
Analog to digital conversion is implemented with a 12 bit converter, having 11 multiplexed
analog inputs and a serial digital data output. This function is controlled by an isolated
microcontroller, which also controls the configuration and operation of the various sub-
circuits. This processor is an 8 bit low power microcontroller with parallel I/O capability.
The isolated microcontroller communicates in a serial format with the non-isolated
microcontroller via opto-couplers, from which it receives its operational information, and to
which it sends the patient data and circuit status.
The non-isolated microcontroller is a high-performance 32 bit integrated processor with
direct memory access.