Panametrics CGA 351, Руководство пользователя, Страница: 68 / 119

Chapter 4.
62 CGA 351 User’s Manual
4.1.14 Calibrating the CGA 351
To calibrate the CGA 351 analyzer, the following steps must be completed:
•
introduce the chosen calibration gas
• regulate the calibration gas flow rate
• adjust the calibration setting as required
Proceed with the instructions in this section to calibrate the analyzer.
4.1.14.1 Recommended Calibration Gas
To properly calibrate the zirconium oxide oxygen sensor, a calibration gas of known composition must be used. The
following calibration gas is recommended by the factory:
• 5 ppm O
2
in N
2
IMPORTANT: The gas cylinder must be certified as to the exact composition of the calibration gas.
A calibration gas containing only CO is not recommended, since the analyzer will not respond correctly to dry
calibration gases that do not contain H
2
. However, CO may be used if moisture is added to the gas by passing it
through a saturator or bubbler.
Uncertainty in the oxygen content of the calibration gas may be a significant source of error in the calibration
process. A standard certificate of analysis has an uncertainty in the smaller component of ±5%. For the
recommended calibration gas, this means an oxygen range of 4.5–5.5 ppm, and the corresponding potential
calibration errors shown in Table 113 below are introduced.
As shown in Table 113 above, a calibration uncertainty of about ±0.95% is introduced by the calibration gas
uncertainty alone.
Table 113: Calibration Uncertainty
ppm O
2
T(°C) mV

mV %Error
4.5
700
225.317 +2.209 +0.99
5.0 223.108 0.00 0.00
5.5 221.110 –1.03 –0.90