User Manual SERVOPRO Plasma Trace N
2
Analyzer
7.0 OPERATION
The following figure shows this sub-menu:
FIGURE 7: CALIBRATION SUB MENU
The display shows the actual ppm of nitrogen value and the actual flow in cc. If the unit is started
up for the first time or you replace the calibration gas with a new value, the ppm display has no
meaning. This can be zero or off scale.
In order to calibrate the unit properly, all lines and regulators on the calibration cylinders must be
completely purged. Allow the zero gas to flow into the analyzer. After 10 minutes of the zero gas
flowing into the analyzer, select "F1" on the keypad. You will be asked for a confirmation to re-
zero, select "YES", at this moment this message will be replaced by "PLEASE WAIT",
indicating the sampling of the analog input. This message is displayed for 5 seconds.
NOTE: an indicator is displayed on the right of the confirmation message informing the user if
the re-span or the re-zero has not been performed yet.
After this delay, the "ZERO DONE" message is displayed. Now, allow the span gas to flow into
the analyzer for 10 minutes or until the displayed measure value is very stable. Select "F2" on
the keypad. Again, you will be asked for a re-span confirmation, select "YES", at this moment,
again, this message will be replaced by "PLEASE WAIT" on the display for a certain amount of
time. When this step is done, the "SPAN DONE" message is displayed; the span gas value is
shown on the left corner of the display. Recheck zero and, if necessary, calibrate a second time.
When the calibration procedure is finished, go back to the CALIBRATION MAIN MENU by
pressing "F4" on the keypad. From the CALIBRATION MAIN MENU, select "F4" again to
go back to the MAIN MENU ("TOP LEVEL MENU").
7.2.1. Important facts concerning calibration
With today's technology of Argon production, total impurities in argon are below 1 ppm. It is
difficult to obtain reliable calibration gases with low ppm value. For example, to calibrate in
range 1 with a calibration cylinder one would require a zero gas containing around 0.2 ppm and a
span gas containing 0.8 ppm. In practice, many users have discovered that zero gases were
giving higher cell counts than the span gases. There are many reasons for this: the mixture can
be wrong or the cylinder may have been contaminated when installed. Bad purging procedures
will shift the calibration cylinder by many orders of magnitude. The SERVOPRO PLASMA
analyzer can be calibrated in the 0-10 range or in the 0-100 ppm range; and this without affecting
the accuracy on the 0-1 ppm range if the zero gas is really zero. To achieve this, we recommend
<<CALIBRATION FACTORS CALCULATION>>
Measure: 9 PPM Sample Flow: 25 CC
F1:Zero F2:Span F4:RET
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