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Photometric Analyzer Operation /Control Unit 3
Part I 3-21
Teledyne Analytical Instruments
Select zero
mode: AUTO
or
Select zero
mode: MAN
Select whether you want the instrument to do an automatic or manual zero. If
you do an automatic zero, the instrument does the zero by itself. If you do a
manual zero you must manually enter inputs to the instrument to accomplish
the zero, see in the corresponding section of the manual on how these two
functions differ.
When the Enter key is pressed, the following menu will appear:
Zero off: 0.0 ppm
<ENT> to begin Zero
The offset value can be modified by using the Up/Down keys. Next section
shows how to select this value. Suffice to say that whatever value you enter,
will be automatically added to the reading. Thus, if you entered -0.1 ppm, at
the end of the zero the display will show -0.1 ppm.
Once the Enter key is pressed the instrument enters the zero mode. If you
chose AUTO zero mode, the instrument will do the work of bringing the
reading back to zero plus the offset value that was entered. If you chose
MANual zero mode, then you must enter input to the instrument as
explained in the corresponding section of the manual but with one
difference: instead of bringing the display to read zero, you must make the
display read zero plus the value entered as offset.
How the offset value is selected:
To find out what the offset value should be, the intended zero calibration
fluid and the a mix of the process background fluid must be procured. This
of course assumes that the zero fluid and the process background fluid are
very different and that an offset will occur.
1. Let the intended zero calibration fluid flow through the 5000BF sample
cell (this assumes that you have started up you system as recommended by
the manual or technical personnel) and do a zero on the instrument. Leave
the offset set to zero value.
2. At the end of the zero function, make sure the analyser reads zero.
3. Flow a zero level of the process background fluid mix through the
5000BF sample cell on the Analyse mode. Wait for the reading to become
stable. Write the reading down. Change the sign of the reading: This is the