Bio-Rad Model 550, Ultramark, and Benchmark Microplate Reader Accessories - Manual (Page 8)

In general, the on-board software is operated by:
* Pressing MODE and the ARROW keys until the desired mode is displayed.
* Pressing the ARROW keys to choose the parameter to change.
* Pressing SELECT to toggle amoung choices.
* Pressing ENTER to seal the user’s selection.
Calculations
The Microplate Reader uses Beer’s Law to calculate the absorbance value of each well.
Beer’s Law states that absorbance is equal to the log
10
of the ratio of the baseline measurement
intensity (Io) to the sample measurement intensity (I).
Beer’s Law
Absorbance = Log
10
(Io/I)
Before measuring the plate, the reader takes a reading for all eight photodiode channels.
These values are recorded as the baseline measurement (Io) values for each channel, respec-
tively. The reader then records the sample measurement (I) value for each well, and calculates
the absorbance using these values. Channel-to-channel error is significantly reduced because
the Io value for a given channel is used only in determining the absorbance of the wells of that
channel. (The Io values are not averaged.)
Memory Back-up
The battery back-up provides memory even after the plate reader is turned off. The fol-
lowing information will be saved in the memory until a new plate is read by the instrument.
Note that if reading a new plate is aborted before it is finished, all the previous data remain
in memory and none of the data from the new plate are retained.
1. Last plate reading data (absorbances for all 96 wells)
2. Reading mode
a. Single or dual wavelength
b. Measurement filter position
c. Reference filter position
d. Plate mixing Yes/No
3. Report types selected
4. Blank well locations
5. Limit values
6. Cutoff report parameters
a. Report type (Constant or Formula)
b. Cutoff constant value
c. Control well locations for formula cutoff
7. Concentration report parameters
a. Number of samples and sample replicates
b. Standard concentration values
c. Number of standards and standard replicates
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