Datascope Passport 2, Руководство по обслуживанию

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NIBP Module (P/N 0997-00-0501) Theory of Operation
2 - 22 0070-10-0441 Passport 2®/Passport 2 LT™ Service Manual
2.4 NIBP Module (P/N 0997-00-0501)
Overview
The NIBP PCB utilizes a Motorola MC68HC16Z1 microcontroller. This processor is
responsible for controlling a pump and two valves in the generation of the patient pressure
signal. This pressure signal is generated non-invasively using an inflatable cuff. A Fujikura
XFPM-050KPG-P2 pressure transducer converts the pressure signal in the cuff to an analog
voltage. The pressure signal is sampled by an AD7714 24-bit ADC which interfaces to the
microcontroller’s QSPI port. This data is processed by the HC16Z1 to determine the blood
pressure using the oscillometric principle. The results are then fed to the host via a RS-485
interface through the processor’s SCI port.
During a measurement, the HC16Z1 software inflates the cuff and then controls the pressure
bleed rate using a linear valve. The linear valve control allows the software to adjust the
valve orifice to arrive at a nominal linear bleed rate of 6mmHg per second. At the conclusion
of the measurement, a dump valve is opened by the software which allows the cuff pressure
to rapidly bleed down to atmosphere.
A separate Microchip PIC16C710 processor and Fujikura XFPM-050KPG-BP pressure
transducer are used to monitor the cuff pressure redundantly for safety purposes.
This document describes the details of the actual design implementation developed to meet
the specifications set forth in the PCB specification document. It provides theory of operation
and internal specification of this implementation.
2.4.1 Pneumatic System Control
The pneumatic control consists of a pressure transducer, ADC, microcontroller, DAC, and
drive circuitry. This circuitry controls a pump, a dump valve and a linear valve. The
pneumatics can also be disengaged by the over-pressure detection circuitry. The pump is
used to inflate the cuff at the beginning of each measurement cycle. Inflation pressure is
regulated by the HC16Z1 software monitoring the pressure transducer signal from PT1 via
the AD7714 ADC.
During the pump-up phase, the dump valve (V1) is closed and linear valve (V2) is modulated.
At the onset of the actual measurement phase, the linear valve is controlled to provide a
gradual reduction of the cuff pressure. The HC16Z1 software maintains the pressure bleed
rate at a nominal 6 mmHg per second, regardless of the cuff pressure or system volume.
During the measurement phase, the pressure signal acquired by the transducer PT1 is
digitized by the ADC (U2) and processed to extract the oscillometric blood pressure data. At
the conclusion of the measurement phase, the dump valve and linear valve are both fully
opened to rapidly exhaust the residual cuff pressure.