Eppendorf AF2200 Plate Reader - Manual (Page 39)

Operation
Eppendorf ® PlateReader AF2200
English (EN)
39
6.2.4 Multi mode measurements
The software offers multimode measurements. This means that 10 measurements can be conducted for
each plate/plate area (pattern) in the "Absorbance" or "Fluorescence intensity" modes, or in a combination
of the two modes.
6.2.5 Ratio mode measurements (= measurements well by well)
The well-by-well processing of one or several measurements is limited to 4 consecutive measuring strips of
the same mode.
6.3 Optimizing fluorescence measurements
The results of the fluorescence measurement can be optimized by adjusting the following device
parameters or selecting suitable materials.
6.3.1 Gain settings
The fluorescence detection system uses an ADC (analog digital converter) conversion of the PMT signal.
The signal gain controls the amplification of the PMT signal during the conversion of fluorescent light into
electric current. The ADC requires a sufficiently high PMT current as well as linearity in order to generate a
suitable signal-to-noise ratio (S/N). Therefore, the signal gain should be set in such a way that the wells
which contain the samples with the highest concentration yield the highest fluorescence intensity signal
possible, i.e. PMT output current. Then, the results of the wells in microplates with lower concentrations
should still be higher than the background signals.
6.3.2 PMT properties
The signal amplification of the fluorescence intensity can be selected in a range of 1 – 255. PMT power
depends on the supply voltage. The PMTs are designed for a range of 300 to 1250 V. The dependence of
the signal gain setting and the voltage supply is described in the equation below. The recommended supply
voltage range of the PMT corresponds to signal gain settings between 60 and 255. Signal gain settings
below 60 are possible and can be useful for special applications, but the PMT is not designed for a
permanent supply voltage < 300 V. Eppendorf does, therefore, not accept any responsibility for measuring
results at signal gain settings below 60.
If a well is in "OVER" (overflow) status, you can reduce the gain or select an automatic
amplification (see software manual).
V 1250 *
255
Gain
U =