Siemens FIDAMAT 6 Operating Instructions Manual page 86

Operation
77 Memory -
Analog output
78 Calibration tolerances
5-36
In the event of a fault (S) or CTRL (when the unit is not in measurement
mode),
- the last measured value registered
- or 0/ 2/ 4 mA
or 21 mA
-
is output at the analog output.
The calibration tolerance at the zero point defines in percentage form the
maximum deviation with respect to the smallest measuring span.
The calibration tolerance for span defines in percentage form the
maximum deviation with respect to the current measuring span.
With the aid of this function it is possible to signal changes in the zero
point or span with respect to the last calibration as "maintenance request"
provided a relay output has been configured for "maintenance request"
under function 71.
For this function to be effective the unit must also have been set to "Total
calibration" (function 22).
The calibration tolerance, which can be set between 0 – 99%, relates in
the case of the zero point to the smallest measuring range span, and in
the case of the span to the measuring range span in which total
calibration is carried out.
Let this be made clearer with the aid of an example:
Measuring range 1:
Measuring range 2:
Smallest measuring span:
Measuring range in which
calibration is carried out:
Response threshold for zero point 95 ppm THC x 10% = 9.5 ppm THC
Response threshold for
span
If the zero point (or the span) now deviates with respect to the last
calibration performed by more than the configured value, the
corresponding relay with signal a maintenance request.
5 ... 100 ppm THC
20 ... 200 ppm THC
95 ppm THC
Measuring range 2
180 ppm THC x 10% = 18 ppm THC
FIDAMAT 6 gas analyzer
Operating manual –A5E00222135-01