Horiba Scientific FluoroMax-4 Operation Manual page 90

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FluoroMax -4 & FluoroMax -4P with USB rev. D (30 Jul 2012)
Determining the optimum integration time
The length of time during which photons are counted and averaged for each data point
is referred to as the integration time. An unwanted portion of this signal comes from
noise and dark counts (distortion inherent in the signal detector and its electronics when
high voltage is applied). By increasing the integration time, the signal is averaged long-
er, resulting in a better S/N. This ratio is enhanced by a factor of t
tiplicative increase in integration time. For example, doubling the integration time from
1 s to 2 s increases the S/N by over 40%, as shown below:
For an integration time of 1 second,
S / N
Because S/N determines the noise level in a spectrum, use of the appropriate integration
time is important for high-quality results.
To discover the appropriate integration time:
1
Find the maximum fluorescence intensity by ac-
quiring a preliminary scan, using an integration
time of 0.1 s and a bandpass of 5 nm.
2
From this preliminary scan, note the maximum
intensity, and select the appropriate integration
time from the table below.
Signal intensity (counts per second) Estimated integration time (seconds)
1000 to 5000
5001 to 50 000
50 001 to 500 000
500 001 to 4 000 000
Note:
measurements, such as time-base, polarization, phosphorescence lifetimes,
and anisotropy, may be different.
Set integration time through Experiment Setup for a specific experiment, or Real Time
Control to view the effects of different integration times on a spectrum. See the
FluorEssence™ on-line help to learn more about setting the integration time.
1 2 /
t
1 2 /
1
1
This table is only a guide . The optimum integration time for other
1/2
For an integration time of 2 seconds,
1 2 /
S / N t
1 2 /
2
. 1 414
or approximately 42%.
2.0
1.0
0.1
0.05
5-8
Optimizing Data
, where t is the mul-