GDS GASMAX II, Руководство по эксплуатации и обслуживанию

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GASMAX II Operation & Maintenance Manual, Revision 7.0
Page 29
5 CALIBRATION
CALIBRATION OVERVIEW
Calibration is critically important to ensure correct operation of the GASMAX II. The built-in CAL MODE
function is designed to make calibration quick, easy and error free; a successful ZERO and SPAN
calibration requires only four keystrokes.
During CAL MODE the sensor output is disabled and the GASMAX II transmits a fixed mA value, called the
CAL MARKER, to notify the receiving device that a calibration is in progress. During the following CAL
PURGE DELAY time, the GASMAX II transmits a fixed 4.0 mA signal to prevent external alarms during
calibration. In the case of local or remote Oxygen sensors, during CAL PURGE DELAY the output simulates
a typical atmospheric reading of 20.8%. CAL MODE automatically exits if no keystrokes are detected after
5 minutes.
Follow these GASMAX II calibration guidelines:
•
Calibration accuracy is only as good as the calibration gas accuracy. GDS Corp calibration gases are
traceable to NIST (National Institute of Standards and Technology).
•
Never use calibration gas that has passed its expiration date.
•
Check the SPAN GAS VALUE setting and make sure it matches the calibration gas. (See Fig. 6-2)
•
Always use a GDS Corp calibration cup that completely surrounds the sensor head.
•
Be sure to use ZERO AIR, a mixture of 21% oxygen and 79% nitrogen, as a zero reference unless you
are cer
tain that no target gas exists in the area. mbient gas may result in an ‘elevated zero’
condition that will cause a FAULT to occur once the ambient gas is no longer present.
•
Always calibrate a new sensor before depending on the device for personnel or equipment safety
•
Calibrate on a regular schedule. GDS Corp recommends a full calibration every 3 months, with
periodic ‘bump tests’ on a more frequent basis to ensure that the sensor has not been affected by
temperature extremes or the presence of incompatible gases.
Figure 5-1: Calibration Flowchart