Chapter 6
Calibration
6.1
General Information on calibration
Messkonzept uses gases with the following purities for calibration:
H2
He
N2
Ar
O2
CO2
CH4
5.0
5.0
5.0
4.6
4.5
4.5
4.5
The gas purities are selected such that the devices comply with the specifications for the smallest
measuring range. Messkonzept recommends gases of same purity for calibration on-site. For
differing individual requirements, opt for an appropriate gas purity. Please contact us for advice.
We recommend a calibration, resp. a check of the calibration if one of the following criteria is met:
• After bringing the device into service
• On a regular cycle, depending on the precision aimed for. To find out the appropriate time
between calibrations, we recommend to begin with a more frequent check of the calibration.
The time between calibrations can range between:
–
several month for a measuring task in the Vol.% range
–
days to weeks for a measuring task in the sub-Vol.% range
–
to directly before every measurement if highest accuracy is needed
• When the situation of the measurement regarding pressure or gas flow changes in case an
extreme change in ambient temperature occurs
For devices operated in “safety mode“, the operator code is required to access the calibration
menu. By default the operator code is set to 111.000. The goal of the calibration is that the
measured concentration is in agreement with the given test gas concentration. To obtain this,
two calibration parameters that correspond to the gain and the offset of a linear equation are
available. A two-point calibration requires two test gases. Both calibration parameters, offset and
gain, are adjusted. The concentration of the test gases does not have to meet the beginning
and the end of the measuring range, a difference of
±
10% is permitted. The menu sequence
is designed such that prior to a gain always an offset calibration has to be done first. Usually a
single point calibration determining a new offset value is sufficient to obtain a good calibration.
In this case a test gas of any concentration in the measuring range is feasible. For two point
calibrations it is preferable to use the lower concentration for the offset calibration and the higher
concentration for the gain calibration.
File name: Manual_FTC400_1.09KD181129CWI1V01.pdf
