Teledyne BDS-3000 - Oxygen analyzer User Manual
Page 64
Operation
BDS 3000
Teledyne Analytical Instruments
50
oxygen content of the sample gas is higher than 0.1 ppm, a zero gas such
as nitrogen having an oxygen concentration below 0.1 ppm may be
required.
4.4.1
Zero Cal
The BDS Sensor has a zero offset of less than 5 ppb oxygen.
Normally, the offset slowly decreases during the first 7 to 10 days of
operation, and is expected to reach a steady value after this time.
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 5 ppb oxygen may include 0.4 ppm oxygen in the sample gas
and a 5 ppb 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 0.1 ppb.
The user may decide to eliminate the zero offset for improved
accuracy. If so desired, the analyzer is equipped to provide this
function. However, we do not recommend carrying 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 acceptable 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 A
UTO
M
ODE
Z
EROING
Press ZERO to enter the zero function mode. The screen allows you
to select whether the zero calibration is to be performed automatically or
manually. Use the __
arrow keys to toggle between
AUTO
and
MAN
zero settling. Stop when
AUTO
appears, blinking, on the display.
Zero: Settling: AUTO
Press ENTER to begin zeroing.