Metrohm tiamo 2.3 Patch 1 (process analysis) - Manual (Page 1646)

7.20 IO controller ￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
1630 ￭￭￭￭￭￭￭￭ tiamo 2.3 Patch 1 (for Process Analysis)
Example
In the given switching example, one would actually like to remain
between 7 and 17 mA. To accomplish this, the following values must be
entered as lower limit and upper limit:
(7 – 4)/0.8 = 3.75 mA
(17 – 4)/0.8 = 16.25 mA
ARW only with I may not then be selected under these circumstances.
The controller starts running at the value 0 after the parameters have been
set. Particularly in cases of asymmetrical value ranges such as are found in
the example, this can be extremely awkward, because it first has to run
for a while before it is able at all to get outside the negative limitation. For
this reason, it is expedient in such situations to use a different (here:
larger) offset and/or slope and correspondingly adjusted limits to achieve a
situation in which the controller is already in a useful status at the time of
switch-on status and can begin controlling immediately. The question of
which values are expedient here is however dependent on the concrete
application and the associated set of parameters can be determined with
the method communicated in the example.
If the output value exits the value range of the 16-bit terminals, then it will
automatically be limited to this range. In the case of the above-mentioned
12-bit terminals, this mechanism does not engage correctly. If values fall
below the lower limit, limitation will be correct; if the range is exceeded in
an upward direction, then the value range will however be mirrored once
again. This leads to large actuating variables in the output value in the
event of incorrect limitation by the controller and to non-functioning con-
trol. The parameterization of the limitation is for that reason to be particu-
larly observed with these terminals.
7.20.8.1.6 Properties - PID controller
Dialogfenster Configuration ▶ Devices ▶ [Edit] ▶ Properties... ▶ Properties - 'De-
vice type' - 'Device name' ▶ Controller ▶ [Edit] ▶ Properties - 'Controller type'
Controlled variable
Selection of the controlled variable from out of all analog inputs or selec-
tion of a calculated value.
Selection 'Port description' | Calculated value
'Port description'
All analog input ports can be selected.
0% Mapping
Measured value to be used when the Low level (0%) is applied as input
value.