Technical Manual
–
Central Operation Unit Smart
MDT technologies GmbH •
51766 Engelskirchen • Papiermühle 1
Phone: +49-2263-
880 • Fax: +49-2263-4588 • [email protected] • www.mdt.de
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PI control is a continuous control with a proportional component, the P component, and an integral
component, the I component. The size of the P component is specified in K (Kelvin). The I component
is referred to as reset time and is specified in min (minutes).
The control value for continuous PI control is controlled in steps from 0% up to the set maximum
value of the control value.
Max value of control value
The setting "Value of max. control value" can be used to set the maximum value the control value
may assume. To prevent switching operations with large manipulated variables, the parameter
"Value of the max. control value" can be set to a value so that the final control element does not
exceed this maximum value.
Heating/ cooling system
The individual control parameters, P-component and I-component, are set by adjusting the
heating/cooling system used. It is possible to use preset values which are suitable for certain heating
or cooling systems or to freely parameterize the P-controller and I-controller components. The preset
values for the respective heating or cooling system are based on empirical values proven in practice
and usually lead to good control results.
If a free "
adjustment via control parameters
" is selected, the proportional band and reset time can
be freely set.
This setting requires sufficient knowledge in the field of control engineering
.
Proportional range
The proportional band stands for the P-component of a control. The P-component of a control
system leads to a proportional increase of the control value to the system deviation.
A small proportional band leads to a fast correction of the system deviation. With a small
proportional band, the controller reacts almost abruptly and sets the control value almost to the
maximum value (100%) even with small control differences. However, if the proportional band is
selected too small, the risk of overshooting is very high.
A proportional band of 4K sets the control value to 100% with a control deviation (difference
between setpoint and current temperature) of 4°C. Thus, with this setting, a control deviation of 1°C
would result in a control value of 25%.
Reset time
The reset time represents the I-component of a regulation. The I-component of a regulation leads to
an integral approximation of the process value to the setpoint. A short reset time means that the
controller has a large I-component.
A small reset time causes the control value to quickly approach the control value set according to the
proportional band. A large reset time, on the other hand, causes the output variable to approach this
value slowly.
When making the setting, please note that a reset time that is set too small could cause overshooting.
In principle, the larger the reset time, the slower the system.
Send control value cyclic
With the aid of the parameter "Send control value cyclically" it can be set whether the channel
should send its current status at certain intervals. The time intervals between two transmissions can
also be parameterised.
