Zero (Fresh Air) Calibration
This procedure determines the zero point of the sensor calibration curve. To perform a fresh air
calibration, use the calibration adapter to connect the instrument to a “fresh” air source such
as from a cylinder or Tedlar bag (optional accessory). The “fresh” air is clean, dry air without
organic impurities and an oxygen value of 20.9%. If such an air cylinder is not available, any
clean ambient air without detectable contaminants or a charcoal filter can be used.
At the Zero Calibration menu, you can proceed to perform a Zero calibration or bypass Zero
calibration and perform a Span calibration. You may also go back to the initial Calibration
menu if you want to exit calibration.
l
Press [Y/+] to start calibration.
l
Press [MODE] to quit and return to the main calibration display.
If you have pressed [Y/+] to enter Zero calibration, then you will see this message:
1. Start the flow of Zero calibration gas.
2. Press [Y/+] to start calibration.
Note: At this point, you may press [MODE] if you decide that you do not want to initiate
calibration. This will take you directly to the Calibration menu, highlighted for Span
calibration.
3. Zero calibration starts a 90-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!
or
Zeroing is done!
Reading = 0 ppb Reading = 0 ppm
The instrument will then show the Calibration menu on its display, with Span Calib highlighted.
Handheld PID Monitors 61 User Manual
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