Thermo Scientific Apex Service Manual page 100

AuditCheck™
7-16
AuditCheck™
Components
•
The detector must be equipped with an AuditCheck system.
SETUP
This consists of the 5-way valve, the AuditCheck shuttle tube
with two adjustable airflow valves, shuttle(s) and test sphere(s),
and pneumatic tubing.
Basic Operation
•
The basic operation of the system is as follows. The valve is wired
to a relay under the control of the microprocessor. The valve input
is low pressure air (typically under 30 psi). The two outputs of the
valve go to the AuditCheck tube. The pneumatic system is
plumbed such that the downstream adjustable valve has air
supplied to it. The upstream adjustable valve is not pressurized.
The air pressure forces the shuttle (and test sphere) upstream,
holding it there against the O-ring stop. When it is time to do an
AuditCheck, the 5-way valve is energized, reversing air pressure to
the two adjustable valves. The shuttle is then blown through the
tube in the downstream direction. The 5-way valve is then
deenergized; this returns the shuttle back to the upstream position
ready for the next test.
The signals from most products cannot be completely eliminated
due to a number of factors affecting conductivity of the product.
The important consequence of this fact is the signals from one
individual product are different that the signals from another
individual product of the same type, size, etc. When the signal
from the varying products are added to the signal from the
AuditCheck test sphere (the signal from the AuditCheck test
sphere is very consistent), the signal the detector "sees" varies as
well. The detector is looking for a difference in the AuditCheck
signal during the test and the signal it saw during the learn process.
There are internal limits on how much the difference between learn
and run can be. If the difference is too great, a warning or fault
will be issued. Therefore, the signal the detector "sees" from the
AuditCheck test sphere must be large enough that the differences
in signal from package to package do not appreciably affect the
test function.
The AuditCheck test sphere size is not directly correlated to the
actual size of the test sphere the detector will detect with product.
The primary reason for this is the AuditCheck test sphere is passed
through the detector in a location different from where the product
test sphere is placed. The AuditCheck system is intended to check
the entire system for changes in performance. While there is no
direct correlation of the AuditCheck test sphere size with the
Thermo Fisher Scientific
REC 4258 Rev C