Metrohm tiamo 2.3 (process analysis) - Manual (Page 1640)

7.20 IO controller ￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
1624 ￭￭￭￭￭￭￭￭ tiamo 2.3 (for Process Analysis)
Lower limit Lower limit at which the integration is stopped and the output is limited
(ARW measure).
Note
This is not a guaranteed limit for the total output.
Output slope Following calculation of the actual manipulated variable, the value for the
output at the analog output is multiplied with this scaling factor. The
result must be the correct value for the output.
Note
This value is NOT the factor between the physical value ranges. This lat-
ter multiplies itself in automatically in addition.
Output offset Following calculation of the actual manipulated variable, this scaling offset
is added to the value for the output at the analog output. The result must
be the correct value for the output.
Note
The connection with possibly different value ranges for input and out-
put is to be observed for the interaction between upper/lower limit and
output slope/offset.
Example
A KL3044 (0-20 mA) is plugged in as input and a KL4424 (4-20 mA) as
output. 7-17 is entered, e.g. as the limit. Because of the different ranges
of the terminals, 4 mA suggests itself as an output offset to start. The out-
put slope is usually set at 1. The factor of 0.8 on the basis of the various
physical ranges [(20-4)/(20-0)] arises automatically and is not permitted to
be specified as well.
Because of the fact that the values 7 and 17 still apply before the outlet
modification, the following limits will actually arise:
7·0.8 + 4 = 9.6 mA
17·0.8 + 4 = 17.6 mA
In order to calculate in reverse which limits need to be specified in order
not to go outside of a particular manipulated variable range, the output
offset must be subtracted and then divided by the output slope and the
given physical factor.