Schambeck SFD GmbH
Refractive Index Detector RI2012
RI2012 V1.0 06-2013.EN / 28.10.2013
53
http://www.schambeck-sfd.com
16.3 A
DJUSTING THE OPTICAL SYSTEM
By adjusting the optical system of the RI2012 refractive index detector it is possible to
influence the light intensity reaching the two photodiodes of the light sensor.
To perform the adjustment the sample chamber and the reference chamber of the flow cell
have to be purged with distilled water. When both chambers contain the same liquid
theoretically the same light intensity should reach the sample side and reference side of the
light sensor. In this case the optical balance should be zero.
The adjustment of the optical system is performed manually. During this procedure the
position of the light beam on the photo sensor is changed by adjusting the mirror.
During the procedure you can follow the changes by observing the change of the detector
signal or more detailed by observing the difference and sum voltage.
For the calculation of the different voltages, the detector signal and the optical balance the
following formulas are used:
Rfrn
Smpl
Diff
Rfrn
Smpl
Summ
00
00
1000
Summ
Diff
OB
AZ
C
OB
POL
Signal
0
Where Signal is the calculated detector signal, POL the selected polarity, C
0
is the
calibration factor resulting from the 3-step-
calibration and AZ the ‘real’ signal before
pressing the AutoZero button.
The pre-set calibration factor is 2724. This factor is used if no 3-step-calibration of the
instrument was performed.
To adjust the optical system follow the steps listed below.
Switch to purge mode, make sure the red purge LED is on.
Flush both chambers of the flow cell with clean mobile phase for several minutes.
Switch back to measuring mode, make sure the red purge LED is off.
Remove the cover from RI2012
The optical system is in the extra housing.
