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Four-loop programmable controller

Author : M Babb

04 September 2009

The trend in industrial control is to combine as much as possible into a single package. GEFRAN accomplishes this with its GF_PROMER, which is a time-variable setpoint programmer, 4-loop controller, graphic trend and bargraph display, all in a single device with data saving functions.

GEFRAN GF_PROMER
GEFRAN GF_PROMER

The user interface, based on an LCD TFT colour touch screen (3.5 and 5.7 inch), is extremely simple to use. Both sizes are shown in the photo.

Menus and programs
Configuration menus are identified by keys and icons that give immediate access to work program creation pages.


Every program is identifiable with a number and a name, a time base definable in days/hours, hours/min, min/sec, and different start and stop strategies. In addition, a number of cyclical repetitions of the program can be set.


The steps are configured the same way with numbers and name, with up to four setpoint values for the four available loops, and step duration in the time base for the selected program.
Cyclical repetitions of a sequence of contiguous steps can be easily created.


When a program has been created, it can immediately be displayed in trend form to intuitively display correctness of the programming.

Running and monitoring the program
The program is selected from the programs list (from screen or digital inputs) and the Monitor page is automatically called up, from which all of the main process data are controlled.

The monitor page is divided into two parts and simultaneously shows, in trend form, the trend of controlled variables (at the left of the screen) and of programmed setpoints (on the right).
The real-time data are at the centre of the page.


The top of the page shows the program name and run state, plus lapsed and remaining time.
The monitor page can be adapted to display what the user needs to see at any time: buttons let the user display / hide trend tracks, while a zoom key allows expansion of the time base to the value required.


States of enable inputs and event outputs are displayed graphically for each step being run, and the steps are highlighted by name or number on the screen.


Control loop engineering scales are independent and each value can be represented on graphs and bar graphs.

Special displays and functions
The “Hold Back Band” function, independently settable with different values for each step of each control loop, checks that the variables trend remains in the defined tolerance “window,” blocking execution of the program if maximum deviation is exceeded.


Bargraph display pages for channels offer immediate data on analogue indicators, with different colours to identify heating and cooling phases, and deviation between PV and SP, while a specific bargraph displays output power level.


These pages are also adaptable to the application via buttons, which display zones freely from 1 to 4.


Under the conditions required, manual variations of setpoint, supplied power, and PID values can be made on the page for each zone.


GF_PROMER provides complete alarms control, with recognition functions, protection of the entire application based on various password levels, and saving of historical data, programs, and settings with the USB key.


The choice of “distributed” or “centralised” control architecture makes GF_PROMER flexible and adaptable to equipment with various performance and modularity requirements.

The controller
Advanced control algorithms provide excellent management of process variables.
Various types of control are available: ON/OFF, P, PI, PID both only heat or cool and double-action heat+cool.


In addition, the cool action can be set via indication of the cooling fluid used: air, oil, or water.
The calculation of the most appropriate process parameters is extremely rapid and efficient thanks to the use of sophisticated automatic tuning procedures.


Advanced tuning lets users check the best PID parameters under all conditions.

Alarms
There are two alarm setpoints (minimum and maximum) for each zone.
For each alarm, the user can select:
* The control variable to assign to it
* Setpoint value
* Hysteresis value
* Five properties (with latch, disable at switch-on, normal/symmetrical, absolute / deviation, direct/inverse).
The user can set LBA (Loop break alarm), HB (Heater break), SBR (Sensor break) alarms: alarm presence is displayed with an icon and described on the alarms page.


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