Offset Absorbance; Blank - Awareness Technology Stat Fax 4700 Operator's Manual

2.5.1.2 Offset Absorbance

If Differential Filter is set to "None", then the Offset Absorbance field is displayed.
Figure 2.5.1.2-1Test Definition – Offset Absorbance field displayed
The user should determine the value of the Offset Absorbance. This value will be
subtracted from the absorbance readings to correct for the meniscus effect for the test that
is being run. Select the Offset Absorbance field and enter the user-determined offset
absorbance value. Press the Save button to save the settings.
Offset Absorbance feature is only needed when both of these conditions occur:
• Monochromatic reading
• No blank well
It is a mathematical blank to correct for the differential between air and liquid with a
meniscus.
To determine the user-entered value, pipette a volume of wash buffer into a well that is
equal to the total volume in test wells at the read time.
For example, if the well has 100µl of Substrate Part A per 100 µl of Substrate Part B, plus
50µl of stop solution, the total volume in the test wells at the read time is 250µl. Therefore
read the absorbance of 250µl of colorless wash buffer to determine the correct value for
the Offset Absorbance. Typical values are from .250 to .400A.

2.5.1.3 Blank

The Test Definition Blank screen will display when the Blank field is selected. This screen
allows for the Blank setting to be enabled (Yes or No); and for inputting the number of
Replicates. Press the Done button when editing is completed
30 Stat Fax
TEST DEFINITION
Name
Absorbance
Mode
Primary Filter
Differential Filter
Blank
Offset Absorbance
Print Save
TEST DEFINITION Blank
Enabled
# Replicates
Range Low
Range High
Figure 2.5.1.3-1 Test Definition Blank display
® 4700 Operator's Manual Doc. 4700 Rev. G
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