Teledyne 6650 - Fluorescence Probe - Oil in Water analysis system - Manual (Page 28)

Setup & Operation Model 6650
20 Teledyne Analytical Instruments
USR SPAN CONTROL to adjust the display to read 1000
counts
6) Adjusting the display level after Mode 2 initialization is not
recommended
5.6 Adjusting the 20 mA Level
The zero level or 4 mA level can be adjusted at any time during the
monitoring process; however, it is strongly recommended that the 4 mA
level be adjusted when the fluorescence probe is immersed in the
background sample. The Fluorometer/probe combination exhibits a
fluorescence signal so even if the background material does not
fluoresce and there is not stray light in the measurement area there will
be a non-zero fluorescence measured. It is not critical that the
background fluorescence be zero, only that the background fluorescence
level is stable. Furthermore, the zero fluorescence level is set
electronically in both Mode 1 and Mode 2, not by process samples.
The following procedure is followed for both Mode 1 and Mode 2
initialization. Refer to Figure 3-1 for the locations of the adjustments
discussed.
1) Immerse the probe in a process sample, preferably the
background material with no analyte of interest.
2) Monitor the 4-20 mA signal using an appropriate meter.
3) Note the display reading.
4) Depress and hold the ZRO CHK button. This disconnects
the Fluorometer output from the detector circuitry of the
Fluorometer, which allows the 4 mA level to be set.
5) The display should read approximately 0000 ± 20 counts
and the 4-20 mA signal should be 4.000 ± 0.164 mA.
a) Adjusting the Display
i. Changing the display once ZRO CHK is depressed
will only alter the display level observed once ZRO
CHK is no longer depressed.
ii. The display adjustments are located to the left of the
display. If the display reading is close to 0000 counts
(<100 counts off) use the FINE ZERO CONTROL to
adjust the display.