Trace Oxygen Analyzer Operation 4
4-13
Teledyne Analytical Instruments
Zero: Settling: Man
<ENT> To Begin
Press Enter to begin the zero calibration. After a few seconds the first
of five zeroing screens appears. The number in the upper left hand corner is
the first-stage zero offset. The microprocessor samples the output at a prede-
termined rate. It calculates the differences between successive samplings and
displays the rate of change as Slope= a value in parts per million per second
(ppm/s).
#### ppm Zero
Slope=#### ppm/s
NOTE: It takes several seconds for the true Slope value to display. Wait about
10 seconds. Then, wait until Slope is sufficiently close to zero before
pressing Enter to finish zeroing .
Generally, you have a good zero when Slope is less than 0.05 ppm/s
for about 30 seconds. When Slope is close enough to zero, press Enter. In a
few seconds, the screen will update.
Once zero settling is completed, the information is stored in the
microprocessor, and the instrument automatically returns to the Analyze
mode.
4.4.1.3 Cell Failure
Cell failure in the 3000TA-XL is usually associated with inability to
zero the instrument down to a satisfactorily low ppm reading. When this
occurs, the instrument will still Zero, but the 3000TA-XL system alarm trips,
and the LCD displays a failure message.
#.# ppm Anlz
CELL FAIL/ ZERO HIGH
Before replacing the cell:
a. Check your span gas to make sure it is within specifications.
b. Check for leaks up-stream from the cell, where oxygen may be
leaking into the system.
If there are no leaks and the span gas is within specification, replace the
cell as described in chapter 5, Maintenance.