Yokogawa Single Channel Oxygen Analyzer System ZR22/ZR402 - Manual (Page 141)

IM 11M12A01-03E 9-5
9. Calibration
Figure 9.3 shows a one-point calibration using only a span gas. In this case, only the cell
electromotive force for a span gas with oxygen concentration p1 is measured. The cell
electromotive force for the zero gas is carried over from a previous measurement to
obtain the calibration curve. The principle of calibration using only a span gas also
applies to the one-point calibration method using a zero gas only.
21.0 p1 0.51
81.92
ez
e1
es
0
C
A B
Zero-point correction factor = (B/A) x 100 (%) Correctable range: 100
±
30%
Span correction factor = (C/A) x 100 (%) Correctable range: 0 ± 18%
Cell
electromotive
force, mV
Calibration curve before
correction
Previous
zero-gas data
Corrected calibration curve
(theoretical calibration curve)
Zero origin
Span origin
Span-gas concentration
Oxygen concentration (vol%O 2 )
F9.3E.EPS
Figure 9.3 Calculation of a One-point Calibration Curve and Correction Factors
using a Span Gas
9.1.4 Characteristic Data from a Sensor Measured During Calibration
During calibration, calibration data and sensor status data (listed below) are acquired.
However, if the calibration is not properly conducted (an error occurs in automatic or
semi-automatic calibration), these data are not collected in the current calibration.
These data can be observed by selecting the detailed data display key from the basic
panel display. For an explanation and the operating procedures of individual data,
consult Section 10.1.1, “Detailed Display.”
(1) Record of span correction factor
Recorded the past ten span correction factors.
(2) Record of zero correction factors
Recorded the past ten zero correction factors.
(3) Response time
You can monitor the response time provided that a two-point calibration has been
done in semi-automatic or automatic calibration.
(4) Cell’s internal resistance
The cell’s internal resistance gradually increases as the cell (sensor) deteriorates. You
can monitor the values measured during the latest calibration. However, these values
include the cell’s internal resistance and other wiring connection resistance. So, the
cell’s degrading cannot be estimated from these values only.
When only a span calibration has been made, these values will not be measured, and
previously measured values will remain.
(5) Robustness of a cell
The robustness of a cell is an index for predicting the remaining life of a sensor and
is expressed in a number on four levels.