84 DF-310E User Interface
conditions (4" Hg vacuum or higher), such as when taxing the capability of the on-board pump,
the Analyzer should be calibrated with the pump operating even if the calibration gas has
sufficient pressure to preclude the use of the pump. The operating pump will create a pressure
condition at the sensor that simulates the operating condition.
Analyzers with a pump are fitted with two flow control valves, one on the downstream rotameter
and one on the sensor inlet (upstream of the sensor). Before turning on the pump, open the
rotameter valve fully by turning it counter-clockwise. Close the upstream flow control valve
completely (clockwise). Set the calibration gas regulator to less than 10.0 psig, then attach the
calibration gas line to the Analyzer inlet. Use the upstream flow control valve to set the flow
rate to 1.0 scfh. Turn on the pump and readjust the flow rate prior to calibrating.
NOTE
Do not adjust the valve at the rotameter, leave it in the fully open
position during calibration.
For an accurate calibration, the sensor output must be stable. The time to achieve stability
depends on the range of the Analyzer and the difference between the sample gas value and the
span gas concentration. Typically, lower ppm range instruments require more time to achieve a
stable output than higher ppm or percent instruments. The use of a chart recorder is suggested to
monitor stabilization.
NOTE
Time required for the O
2
reading to stabilize when on span gas can
vary from 15 to 60 minutes.
After a stable reading is obtained, enter the O
2
concentration of the calibration gas. Then press
to complete the calibration.
A “Wait...” message will appear, followed by the display shown in Figure 54.
Figure 54: Calibration Convergence Screen
It may take several minutes before convergence occurs. During convergence, the Analyzer is
verifying stability of the reading before accepting the data. After convergence two short beeps
will be heard. The Analyzer's electronics can be updated to the new calibration information by
selecting Update and Quit.
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