Michell Instruments XZR-400-BM, Руководство пользователя

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XZR400 Series User’s Manual
Michell Instruments 55
CALIBRATION
4.1 Defi nitions
• Adjustment gas: an adjustment gas used in order for the analyzer to
correct a possible difference between the measured value and the actual
O
2
content in the gas. The value which is written on the cylinder (or on
the relevant analysis certi fi cate) must be entered in the fi eld
adjustment
gas
section. The content can be in either % or ppm.
• Control gas : a gas with a different O
2
content than the adjustment gas.
It helps in verifying the calibration. The O
2
content can be either in % or
ppm. This control is not compulsory.
• Process gas : the gas to be measured.
• Calibration duration : the period during which the adjustment gas
eliminates the process gas out of the internal sample path. The quality
of calibration will far be greater if the process gas is fully cleared away.
A longer period is necessary when the adjustment gas value is low and/
or when the difference between the process gas and the adjustment gas
is large. Calibration with % level oxygen gas requires approximately 5
minutes. Calibration with ppm level oxygen gas may require 30 minutes.
• Purging time: the period during which the process gas eliminates the
adjustment gas (or veri fi cation gas) out of the internal sample path.
If a low O
2
content (< 1000ppm) adjustment gas is used, a purge
time is necessary to allow the stabilization of the measurement
before starting the calibration sequence. This is even more
important if the process gas is going to be at a very different
concentration from that of the adjustment gas.