WatchGas NEO User Manual page 16

NEO
Photo-ionization Detector
5.4.5 SPAN CALIBRATION
This procedure determines the second (and third, if 3-Point Cal is selected in Monitor
Setup) point(s) of the sensor calibration curve. One or two cylinders 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. The span gas concentration should be
chosen to be near the highest concentration of actual measurements expected. It is
also preferred to use the same balance gas (e.g., air or nitrogen) as occurs in the actual
measurements.
To perform a Span calibration, connect the calibration adapter to the inlet port of the
instrument, and connect the tubing to the regulator or gas bag. Select 'Span Calib' by
pressing the Right key to enter the submenu. The message 'Please Apply Gas' is displayed.
Start the gas supply and by press the Up key to begin a 30-second span calibration
countdown. The calibration will also start automatically without pressing the Up key if a
high enough gas concentration is detected.
Note: To abort the Span calibration, press the Left key at any time during the process.
The confirmation message 'Span is aborted!' appears followed by the next menu item.
When Span 1 calibration is complete, a message similar
to this is displayed (the value is an example only):
5.4.6 3-POINT CALIBRATION
If '3-Point Cal.' is enabled (see Monitor Setup), proceed to perform Span 2 in the same
manner as for Span 1.
3-Point calibration should be used whenever enhanced accuracy is required. It is especially
recommended for measurements above about 500 ppm, where PID response is not quite
as linear.
5.4.7 SET CALIBRATION GAS
In the Set Cal. Gas menu, select the calibration gas from either the WatchGas Gas Library
or the user's Custom Gases list. Custom Gas names and parameters can only be set up
through the WatchGas Suite software.
16
Span 1 is done!
Reading = 10.ppm