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

7.20 IO controller ￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭￭
1630 ￭￭￭￭￭￭￭￭ tiamo 2.3 (for Process Analysis)
Description of the mode of operation
The controller uses an internal PWM module which is used for activating
the actuator. The pulse-pause ratio of the PWM module is adjusted adap-
tively to the behavior of the control process. The PWM output is switched
on as soon as the control deviation E = setpoint value minus actual value
greater than zero, and switches off when the control deviation is less than
zero. As long as the control deviation is within the interval ( – tolerance
range ... tolerance range), the pulse-pause ratio will not be changed. If E is
> than the tolerance range, then the pulse-pause ratio will be increased by
one step. After this elevation, the system will wait out the control delay
time before the pulse-pause ratio is possibly altered once again. In the
event that the level falls below the – tolerance range, the pulse-pause
ratio will be reduced by one step. The pulse-pause ratio is varied only
within the interval [fMinLimit ... fMaxLimit]. The cycle duration of the
PWM signal can be specified.
E Control deviation; difference of setpoint value minus actual value
Tolerance range Range of fE in which the pulse-pause ratio is not changed.
Working area If fE is exceeded in this range, then the output signal will be set perma-
nently to active.
Cycle duration Cycle duration of the PWM signal. For technical reasons, this should be at
least one order of magnitude over the PLC cycle time of 30 ms. Values
under 30 ms are invalid.
minimum pulse ratio Minimum pulse-pause ratio in percent (0% ... 100%).
maximum pulse ratio Maximum pulse-pause ratio in percent (0% ... 100%).
Step Value by which the pulse-pause ratio is varied with each adaptation
(0% ... 100%). Excessively large values lead to very few possible pulse/
pause ratios. Smaller values cause the controller to react with finer grada-
tions, but also more slowly.
Control delay: Waiting time between the individual variations of the pulse-pause ratio.
Normally these should correspond to at least the cycle duration. Values
under 30 ms are invalid.
7.20.8.1.8 Properties - PWM 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.