System information

4 Absorbance
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Wells marked with a Ref were designated as Reference wells. Reference value of each
wavelength reading is applied to each wavelength reading. If more than one Reference well is
selected, an average of the Reference values at each wavelength is used.
4.5.1 Ratiometric Data
When two wavelengths are selected for a protocol, a reading at each wavelength is taken
for each sample. The results are displayed in OD units in three possible formats.
• When in partial view, reading 1 and reading 2 are displayed side-by-side in the
corresponding well. See Figure 4-4(A).
• When in full view, reading 1 is displayed on top of reading 2 in the corresponding
well. See Figure 4-4(B).
• When the RATIO button is touched, the results are displayed as a single value. See
Figure 4-4(C).
The ratio calculated for absorbance data is different than for luminescence data. The
absorbance ratio is calculated as:
Ratio =
2
nd
reading -1
st
reading
4.6 Absorbance Module
To add absorbance detection capability to the Modulus™ Microplate Reader, purchase and install
the Absorbance Module. See Appendix C for ordering information.
4.6.1 Installing the Absorbance Module
1. Close the instrument door using the DOOR button so that the Microplate Sample
Tray is set at the home position.
2. Power off the Modulus™ Microplate Reader.
3. Manually open the instrument door and hold it down.
4. Hold the Absorbance Module on the fingertips of one hand. Guide the Absorbance
Module into the threaded stainless steel post located on the left side of the
instrument interior. See Figure 4-5.
5. Slide the Absorbance Module into position. Be cautious to not damage the printed
circuit board on the back of the detection head.
6. Hand tighten the two captive screws using the Allen wrench (size 7/16) provided with
the kit. Too much force may damage the screws. See Figure 4-6.
7. Close the instrument door.
8. Power on the instrument.
(A) (B) (C)
Figure 4-4: Absorbance Ratiometric Results as Displayed on the READ
Screen