ASP STERRAD 100, Service Manual

Page: 31 / 309

Output Data
Outputs to the operator include LCD messages, printed messages,
control panel lights, audible beeps, and the opened or closed door.
Digital outputs to the machine’s hardware components are used in every
stage of the sterilization process to perform tasks such as opening and
closing the throttle valve, controlling the RF power, and communicating
with the printer.
100 Millisecond Interrupt
The software runs a 100 millisecond interrupt as its highest priority
interrupt. If the “heartbeat timer” interrupts any segment of the
software, other than the monitor state, the software goes to cancel/abort
processing and provides a controlled failure rather than system lockup.
10 Millisecond Interrupt
In three cases 100 milliseconds is too long for the system to wait
between cycles. For these three areas the software uses a 10 millisecond
interrupt as an interrupt for faster processing:
F
the throttle valve controller
F
the bar code reading
F
cassette positioning mark detector
Software Safety Considerations
The software is designed to shut down certain functions for safety
reasons. These functions are listed below.
F
The output of the RF generator shuts down when faced with
mismatches of greater than 1.5 VSWR to protect personnel from the
RF shock.
F
The door over center sensor is monitored to protect personnel from
hazards.
F
The active low digital output design forces a graceful shut down in
the event of failure in any device or harness.
F
The door remains closed if a power failure occurs during a running
cycle.
F
The door automatically reverses if there is an obstruction of 14 kg
(30 lbs) or more.
F
The RF power can not be activated if the chamber pressure is over
700 mTorr.
F
If a failure occurs, a 10 minute
CANCEL CYCLE
runs to prevent
exposure of the operator to H
2
O
2
vapor.
Theory of Operation-Overview System Operation
ASP Service Guide rev. D STERRAD® 100 Sterilizer 2-15