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Chapter 11
Diagnostics
Self Test
11-10
Introduction
Esprit has an extensive system of checks designed into the system to ensure
that it operates safely and detects fault conditions that can compromise the
performance of the system as a ventilator. These checks include hardware that
checks the integrity of the software and software that checks the hardware to
ensure that it is operating within normal ranges. These checks are described
below.
Self-Test Hardware
The self-test hardware involves hardware components that check the integrity
of the software. The hardware components that perform these checks are the
watchdog timer and the bus activity monitor.
•
Watchdog Timer: The watchdog timer is a timer that the software must
reset. If the timer times out it causes a reset that restarts Esprit as if
the power switch had been turned on. Normally the software resets the
watchdog timer and it never times out.
•
Bus Activity Monitor: The bus activity monitor is a timer similar to the
watchdog timer. The bus activity monitor timer is a timer that only
times out if there has been no activity on the microprocessor bus. If
there is no activity on the bus, it would indicate there is a malfunction
of some kind and the Esprit microprocessor is restarted in the same
way that the watchdog timer does.
Power On Self Test (POST)
POST is the test that Esprit does when the machine power is turned on or if
there has been a potential fault detected by the watchdog timer or the bus
activity monitor. POST has the constraint that it must be able to run safely
when Esprit has a patient attached. POST checks the integrity of critical
system electronics such as the self test hardware and microprocessor
electronics. POST also tests other critical ventilator components that can be
tested.
A primary objective of POST is to ensure that the watchdog timer and the bus
activity monitor hardware are working and will catch software malfunctions.
These are critical components of the Esprit safety system and therefore POST
tests these components every time it runs.
POST also checks all critical digital hardware, including the processor,
program memory, data memory, and functions of various measurement
systems.
POST also checks pneumatic components that can be safely tested with the
safety valve open.
If all these tests pass, Esprit will operate as a ventilator.
Esprit® Ventilator Operator's Manual © Respironics, Inc.
REF 580-1000-01 Y
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