Rae UltraRAE 3000, User Manual

Page: 54 / 129

UltraRAE 3000 User’s Guide
3. Zero calibration starts a 30-second countdown and displays
this message:
Zeroing...
During the zeroing process, the instrument performs the Zero
calibration automatically and does not require any action on your part.
Note:
To abort the zeroing process at any time and proceed to Span
calibration, press [N/-] at any time while zeroing is being performed.
You will see a confirmation message that says “Zero aborted!” and
then the Span calibration menu appears.
When Zero calibration is complete, you see this message:
Zeroing is done!
Reading = 0.0 ppm
The instrument will then show the Calibration menu on its display,
with Span Calib highlighted.
19.3 Span Calibration
This procedure determines the second point of the sensor calibration
curve for the sensor. A cylinder of standard reference gas (span gas)
fitted with a 500 cc/min. flow-limiting regulator or a flow-matching
regulator is the simplest way to perform this procedure. Choose the
500 cc/min. regulator only if the flow rate matches or slightly exceeds
the flow rate of the instrument pump. Alternatively, the span gas can
first be filled into a Tedlar bag or delivered through a demand-flow
regulator. Connect the calibration adapter to the inlet port of the
instrument, and connect the tubing to the regulator or Tedlar bag.
Another alternative is to use a regulator with >500 cc/min flow but
allow the excess flow to escape through a T or an open tube. In the
latter method, the span gas flows out through an open tube slightly
wider than the probe, and the probe is inserted into the calibration
tube.
52