Teledyne 6200E - Sulfides Analyzer - Manual (Page 249)

Model 6200E Instruction Manual TROUBLESHOOTING & REPAIR
M6200E Rev: A1 249
• Confirm that the H
2
S span gas source is accurate. This can be done by comparing the
source with another calibrated analyzer, or by having the H
2
S source verified by an
independent traceable photometer.
• Check for leaks in the pneumatic systems as described in Section 11.5.1. Leaks can dilute
the span gas and, hence, the concentration that the analyzer measures may fall short of
the expected concentration defined in the
CONC sub-menu.
• If the physical, low-level calibration has drifted (changed PMT response) or was
accidentally altered by the user, a low-level calibration may be necessary to get the
analyzer back into its proper range of expected values. One possible indicator of this
scenario is a slope or offset value that is outside of its allowed range (0.7-1.3 for slope, -20
to 150 for offsets). See Section 11.6.3 on how to carry out a low-level hardware
calibration.
11.3.5. Inability to Zero - No ZERO Key
In general, the M6200E will not display certain keyboard choices whenever the actual value of a
parameter is outside of the expected range for that parameter. If the calibration menu does not
show a ZERO key when carrying out a zero calibration, the actual gas concentration must be
significantly different from the actual zero point (as per last calibration), which can have several
reasons.
• Confirm that there is a good source of zero air. If the IZS option is installed, compare the
zero reading from the IZS zero air source to an external zero air source using H
2
S and SO
2
free air. Check the zero air scrubber for performance. It may need to be replaced (Section
9.3.3).
• Check to make sure that there is no ambient air leaking into the zero air line. Check for
leaks in the pneumatic systems as described in Section 11.5.1.
11.3.6. Non-Linear Response
The M6200E was factory calibrated to a high level of H
2
S and should be linear to within 1% of full
scale. Common causes for non-linearity are
• Leaks in the pneumatic system. Leaks can add a constant of ambient air, zero air or span
gas to the current sample gas stream, which may be changing in concentrations as the
linearity test is performed. Check for leaks as described in fion 11.5.
• The calibration device is in error. Check flow rates and concentrations, particularly when
using low concentrations. If a mass flow calibrator is used and the flow is less than 10% of
the full scale flow on either flow controller, you may need to purchase lower concentration
standards.
• The standard gases may be mislabeled as to type or concentration. Labeled concentrations
may be outside the certified tolerance.
• The sample delivery system may be contaminated. Check for dirt in the sample lines or
sample chamber.
• Calibration gas source may be contaminated.
• Dilution air contains sample or span gas.