PureAire Monitoring Systems, Inc.
2/22/2000
16
5.2.2 Zero Calibration
IMPORTANT:
This procedure should be performed under normal monitoring
conditions, without any of the target gas present.
1.
Check the instrument’s gas concentration reading on the local display.
2. If the display does not read a steady “0,” adjust the zero potentiometer as
required.
Note:
Depending on the gas sensor a clockwise or counterclockwise
rotation increases the value; a counterclockwise or clockwise rotation decreases
the value.
NOTE:
On units shipped through Nov 2008, the digital display does not
display a negative sign. The lowest zero setting will indicate 0.02 or 0.2ppm.
When adjusting zero, turn the pot until the display reading increases, and then
turn it back down until the reading indicates 0.00 or 0.0. This will insure that
you are in the positive range of the display setting.
Units manufactured in 2009 display a negative sign.
5.2.3 Span Calibration
CAUTION:
Be sure to observe all safety guidelines when generating and using
calibration gases.
NOTE:
Gas generation kits are available through PureAire. These kits include
instructions and materials for generating calibration gases and precise methods
for accurately measuring the concentration of these gases.
NOTE:
The gas concentration should be close to, but never exceed, full scale.
1.
Connect the appropriate calibration cap to the inlet of the high flow sampling
pump and connect the Tedlar “waste gas” bag to the outlet of the pump.
2.
Open the valve on the waste gas bag.
3.
Connect the flowmeter to the inlet of the calibration cap and turn the high
flow sampling pump “on.”
4.
Adjust the pump’s flowrate potentiometer until a flowrate of 0.5 liters/minute
(0.2 liters/minute for hydride sensors) is achieved. A clockwise rotation
increases flow; a counter-clockwise rotation decreases flow.
5.
Recheck the instrument’s zero reading; adjust as required.
6.
Generate the calibration gas within a Tedlar bag.
IMPORTANT:
Be sure to perform the calibration before the concentration of
the gas changes. Also, PureAire recommends that you verify that the
concentration of the calibration gas is the same after calibration as it was before.
7.
Disconnect the flowmeter and connect the Tedlar calibration gas bag to the
inlet side of the calibration cap.
8.
Open the valve on the calibration gas bag.
9.
Expose the sensor cell to the span gas for 1 to 2 minutes until the gas reading
stabilizes.
