Teledyne 3000 Ultra Trace - PPB oxygen analyzer - Manual (Page 46)

4 Operation Model Ultra Trace 3000
4-12 Teledyne Analytical Instruments
Generally, the value of the zero offset is part of the oxygen reading of
the sample gas as shown by the analyzer readout. As an example, a reading
of 0.5 ppm oxygen may include 0.4 ppm oxygen in the sample gas and a 0.1
ppm zero offset.
The determination of the zero offset requires the use of oxygen free gas
to the analyzer. We recommend the use of nitrogen gas with a scrubber to
assure oxygen levels below 20 ppb.
The user may decide to eliminate the zero offset for improved accu-
racy. If so desired the analyzer is equipped to provide this function. How-
ever, we do not recommend carying out the cal zero during the first 10 days
of the operation of the cell.
The Zero button on the front panel is used to enter the zero calibration
function. Zero calibration can be performed in either the automatic or manual
mode. In the automatic mode, an internal algorithm compares consecutive
readings from the sensor to determine when the output is within the accept-
able range for zero. In the manual mode, the operator determines when the
reading is within the acceptable range for zero. Make sure the zero gas is
connected to the instrument. If you get a
CELL FAILURE message skip to
section 4.4.1.3.
4.4.1.1 Auto Mode Zeroing
Press Zero to enter the zero function mode. The screen allows you to
select whether the zero calibration is to be performed automatically or manu-
ally. Use the
∆∇
arrow keys to toggle between
AUTO and MAN zero set-
tling. Stop when
AUTO appears, blinking, on the display.
Zero: Settling: AUTO
To Begin
Press Enter to begin zeroing.
#### PPM Zero
Slope=#### ppm/s
The beginning zero level is shown in the upper left corner of the dis-
play. As the zero reading settles, the screen displays and updates information
on
Slope (unless the Slope starts within the acceptable zero range and does
not need to settle further).
Then, and whenever Slope is less than 0.08 for at least 3 minutes,
instead of Slope you will see a countdown:
5 Left, 4 Left, and so fourth.
These are five steps in the zeroing process that the system must complete,
AFTER settling, before it can go back to
Analyze .