Bio-Rad VersaFluor™ Fluorometer - Manual (Page 13)

4.3 Gain Function
Three gain settings are available in the VersaFluor Fluorometer instrument: LOW, MED,
and HIGH gain. There is a ten-fold difference between the gain settings. For example, if the
fluorometer shows a reading of 10,000 RFU on high gain, it will show approximately 1,000
RFU on medium gain and approximately 100 RFU on low gain. The reading range of each
gain setting is between 0 and 19,999 RFU. If the reading is beyond the range of the instrument,
the fluorescence display will show 19,999.
A quick method for determining which gain setting to use is to first set the gain to MED
with the range at 00000. Place a sample with the highest concentration into the instrument
and read the fluorescence display. If the value is below 19,999, then use MED or HIGH gain.
If the value is 19,999, use LOW gain. Some trial and error work may be necessary to deter-
mine the correct gain setting to use.
The user can change gain setting at any time during the sample measurement procedure.
It is recommended to check the zero of the instrument and re-zero if necessary, if the gain is
changed while reading samples. If the samples are read from the LOW gain setting to the
MED gain setting, the MED gain relative fluorescence units should be divided by 10 when
compared to the LOW gain setting units.
To change the gain setting, press the SETUP button in the main menu. Press the GAIN
button to select the gain setting (Figure 4.4). The gain can be toggled between LOW, MED,
and HIGH.
Figure 4.4 Gain setting menus.
4.4 Range Function
The fluorescence units shown on the fluorescence display can be set to a desired value.
The maximum value for the instrument is 19,999 RFU. Adjusting the range will change the
current maximum instrument reading to a different value set by the user. For example, a sam-
ple shows a reading of 4,000 RFU on MED gain, but the user would prefer to see 2,000.
Setting the range to 2,000 will change the current maximum reading to 2,000, and all future
values will also be scaled to the new range. It is important to set a new range value whenev-
er a new fluorescent assay is being performed, because the fluorescent values will be scaled
according to the last sample used to set the range.
Setting the range higher than the amount of fluorescence detected by the fluorometer may
cause some fluctuation in the fluorescence units display. For example, a sample displays a
reading of 1,000 RFU on MED gain, but the range is set to 10,000. There could be a fluctu-
ation in the display by as much as 10 units (background instrument noise times the range
factor of 10).
10
RANGE SET
PRINT 00000 ZERO SETUP
AVRG GAIN
1 SEC LOW
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