Thermo Scientific APEX User’s Guide Page 97
Setting Reject Parameters
This section tells you how to set reject parameters for a typical pharmaceutical
application.
Reject Totals
Understanding Reject-Delay and Reject-Duration Timing
In a pharmaceutical application, the detector’s search head surrounds a chute where
product is falling vertically under the influence of gravity. When the search head detects
metallic contaminants in the product, the product continues down the chute, and is
diverted into a secondary bin by a reject gate. The gate stays closed for a set period of
time (usually about 0.50 seconds) to divert the contaminated product, then opens again
to allow uncontaminated product to again flow freely. Thus, for the reject process to
work properly, two critical time parameters must be set.
• Reject-Delay Time
In most pharmaceutical applications, where the gate is located close to the
search head, the reject-delay time is usually set to 0.00 seconds. Thus, when the
search head detects contaminants, the gate closes immediately.
However, in applications where the gate is located some way from the search
head, a time delay is needed, because the product takes a finite time to move
from the search head to the vicinity of the gate. Clearly, the reject-delay time
should be set to make sure that the gate closes before the contaminated product
actually reaches the gate. Reject-delay times, when needed, are set in seconds
and hundredths of a second.
• Reject-Duration Time
This is the time (in seconds and hundredths of a second) that the gate remains
closed to divert contaminated product into the reject bin. A typical time for a
normal pharmaceutical application is 0.50 seconds.
Once you have set the reject-delay time and reject-duration time parameters, you must
test the reject process.
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