PAC Control

PLC Control

1

COST

Low cost of the life cycle of the system; purchasing, installing, setup, maintaining and upgrading. Operating software is preprogrammed.

Much higher cost per point. Programming is customized in Ladder Logic computer language requiring services of costly programmers.

2

OPERATIONS AND TRAINING

System setup and operation requires only minor training for personnel (included with purchase of:

PCprocess®, PCflow®, PCbrew®).

Systems operations can be complicated requiring extensive training. Proprietary network, communication and programming.

3

Programming

PC programming is accomplished in the graphical interface provided by Microsoft Windows 32-bit platform to present a clear, concise representation of your entire control solution within a single well-documented setting. No Ladder Logic programming required. Foundation of logic: exception based, distributed.

To add features like ASCII communications capability, or complex math functions to Ladder Logic, completely different hardware and programming environments have to be implemented and integrated to support functions that Ladder Logic cannot perform. Program source code required. Continuous scanning.

4

I/O Checking

The I/O units themselves monitor the I/O points and report changes to the controller.  Diverse protocols and open standards.

Every I/O point is scanned cyclically and thus the speed depends on scanning power of PLC. Function and Programming are modeled after relay circuits.

5

Math Functions

Uses 32 bit architecture that easily handles the execution of both integer and floating point math using a library of math functions. Multitasking.

Math functions done by function blocks. (integer only). Expensive add-on cards that require programming in different language and environments if floating point math is needed.

6

P.I.D. Functions

P.I.D. functions are processed by the I/O units, not by the controller. This provides for painlessly expanding P.I.D. loops.  There is NO decline in performance as the number of P.I.D. loops increase. Common tag database..

P.I.D. functions are mostly calculated in the CPU of the PLC.  Calculations needed for multiple P.I.D. loops can quickly bog down the CPU. Mandatory duplication of data tags for interoperability.

7

Scalability

All existing software is compatible. e.g. software on a low-end controller can be loaded and run flawlessly in high-end controllers.

Expanding PLC's may not be an option because the system requirements outgrow the existing PLC capability.

8

Analog

PC's have an intelligent I/O processor on the I/O units for dealing with analog signals. PC's scale and linearize all analog signals, so when values are read there is no need for conversion processing.

PLC's have to execute logic and instructions in the PLC's CPU when dealing with analog signals. These executions and instructions are required to handle the conversion and scaling it receives from the physical I/O of analog values from the raw counts into scaled values.

9

Communications

PC's work well with serial communications and Ethernet and are designed to communicate with third party devices and software available "off-the-shelf".

Serial communications is difficult for PLC's. Multi-function communication PLC's need special purpose hardware that requires knowledge of higher level language than just Ladder-Logic.