< 10. Other Functions >
10-4
IM 11M12D01-01E
10.1.10 Recommended Next Calibration Date
Recording the cell e.m.f. at calibration time, and monitoring the drift in cell e.m.f. with time, gives an
idea of how long it will take for measurement error to reach tolerance, and thus recalibration can be
scheduled before that date. The tolerance is a maximum of ±0.5% of range, so if range is 0-25% O
2
then tolerance is 25% O
2
× ± 0.5% = ± 0.125% O
2
.
The instrument extrapolates a line through the most recent three cell e.m.f. readings (see Figure
10.4), uses this to determine how long it will take for measurement error to exceed tolerance, and
recommends that a recalibration date.
F10-4E.ai
tolerance
2x ago Previous
This
Predicts by extrapolating line through CAL
value 2x ago, Previous and This (present)
Days
Ideal next CAL
Cell e.m.f.
Figure 10.4 Predicting Next Recalibration Date
After the first three calibrations - which, however, must be separated by at least five days, or the data
is ignored by the autopredictor - the autopredictor starts operating.
CAUTION
1) This function does not guarantee accuracy, it’s just a guide.
2) The recommended date for the next calibration with be within the range of between 5 and 90
days.
3) If the predictor finds that the slope of the line becomes positive (the line slants upward to the
right), then it may recommend a next calibration date in five days time.
4) After the predictor has made a calculation, changing the current output range does not affect this
(does not cause a recalculation).
10.1.11 Heater ON-Time Ratio
The probe sensor is heated to and maintained at 750°C. When the sample gas temperature is high,
the amount of heater ON-time decreases.
10.1.12 Time
The current date and time are displayed. These are backed up with built-in batteries, so the clock
continues to run even if the power is switched off.
10.1.13 Ch. card Rev., Ctrl. card Rev.
This shows the revision number of the channel card software and Control card software.
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