Desin Instruments HS-7000 Series, General Instructions Manual

Page: 63 / 108

63
BIMODAL (HEAT-COOL) CONTROL MODE
The Bimodal control is the type of control where the controller produce a doble control action
Reverse or Direct on both sides of the setpoint SP.
If the process variable goes below the setpoint SP, the Bimodal control gives the order to Heat
the process, if the process variable goes over the setpoint SP, the Bimodal control gives the
order to Cool the process, until its stabilization within the Dead Band or Neutral Zone. The
concepts Heat and Cool can define similar actions such as Add or Reduce, Open or Close, etc.
This type of control is suitable for processes generating heat or cool disturbances, to be
controlled by opposite actions.
The
HS-7000 controllers, are provided with bimodal action en every loop, giving direct and
reverse control with independent PID actions to each one of them.
The control outputs can be programmed as:
[Relay- Relay], [4-20 mA - Relay], [Relay- 4-20 mA], [4-20 mA - 4-20 mA], [Step by Step - Step by Step]
HOW TO SET THE PARAMETERS OF A BIMODAL CONTROLLER
●
DEAD BAND:
In the HS-7000 devices , when operating in bimodal mode, the Reverse and Direct Dead Bands
can be adjusted.
The Dead Band are enabled by the parameter
[P 06] of the PID loop, allowing at the same
time, independent adjustment of width of the Direct and Reverse Dead Bands.
The width of the Dead Band should be set between 0.1 % and 1 % of the Span. Never goes
on values over 10% of the Span.
- Dead Band Enabling.
Enter in Parameterization of PID 1 and set [P 06] to [?1??]
- Dead Band Setting.
In Parameterization of PID 1 set:
For Reverse Dead Band
[P 18]
to
[000.1]
0.1 % (recommended)
For Direct Dead Band [P 13] to [000.1] 0.1 % (recommended)
Repeat for loops 2 and 3, in Parameterization of PID 2 and PID 3
●
PID PARAMETERS SETTING:
- Can be done Manually or by Autotuning and fine adjustment with Fuzzy-Logic function, as
explained previously, but adjusting the Reverse PID and Direct PID separately.
IMPORTANT:
- Once the wiring connection is realized, check that the Heat-Cool sequence is correct.
- Check that the LEDs on the front panel are associated to the Heat-Cool actions.