Oxigraf O2iM NEMA 4X Oxygen Analyzer
February 13, 2007 08-0427-B0, Manual, O2iM.doc Page 18
4.4.3 Connecting the Autocal Input to a Source
As an alternative to the use of a pressurized calibration gas as described in the previous section, the
O2iM may be installed with the calibration input connected to a non-pressurized source. This would
typically be a different room or area of the building. Tubing is from the calibration input is routed to
the other source to eliminate the requirement for maintenance of the pressurized calibration gas
system and can eliminate false alarms due to calibration errors caused by inadvertent calibration with
a gas cylinder that has become empty.
Requirements for a remote gas source, non-pressurized:
• Gas source should be clean and dry. This can be accommodated by placing a filter on
the inlet of the tubing that will prevent dust or other foreign objects from entering the
system.
• Additionally, the cal gas inlet needs to be located where there is no possibility of it being
subjected to condensing vapor conditions or submerged. Usually, putting the inlet in a
nearby room where there are no possible sources of liquefied gases and the
environment is maintained by a normal HVAC system does this.
• Gas sources that could affect the quality of the air should not be present. Small
quantities of pressurized gases in a large room will not present a problem for this. Avoid
liquefied gas sources.
• The tubing should be routed and the inlet located so that it will not become kinked or
otherwise blocked.
• Outdoor location of the inlet is NOT recommended.
Advantages of remote calibration gas inlet, non-pressurized:
• Reduced cost of hardware.
• Reduced maintenance requirements.
• Elimination of possibility of calibration errors due to calibration with an empty gas
cylinder. (Causing false alarm)
Advantages of calibration gas, pressurized:
• Traceable gas source.
• Increased absolute accuracy. (By about 0.1%)
Interior air oxygen values:
• Ideal dry air (0% RH) - 20.9% Oxygen
• Comfortable indoor air (40% RH) - 20.7% Oxygen
• Saturated air (100% RH) - 20.4% Oxygen
To Next Page
Loading...
General