UFC 3 -430-11
14 February 2001
4-2.1.2 Programmable Logic Controllers. Programmable logic controllers (PLCs)
are usually programmed in the electrical ladder diagram format. Other formats are also
used. When specifying PLCs include the following features.
Provide a controller that can be programmed in the electrical ladder diagram
format when many logic steps are involved.
Include provisions so that the controller can be programmed and the
program read without disturbing its operation.
4-2.1.3 Controller Configuration. Provide a controller that can be programmed in
any of the following ways at the programmer's option.
From the front of the controller if a separate controller is provided
From a manual control station if a separate controller is not provided
From a configuration device manually
From a configur ation device using stored information from a tape, computer
disk, or other data storage device
Provide either a non-volatile memory or battery back-up for the controller so
that the controller configuration memory is not lost due to a power outage.
4-2.2
Recorders. Keep recorders to a minimum. They constitute considerable
expense in paper and pen replacement costs. If recorders are required then
standardize them so as to keep paper and pen inventory costs to a minimum. Note that
recorders from different manufacturers usually require different paper and pens.
The preferred method of recording data is on computer disks, tapes, or other
data storage device. This data can later be viewed on a monitor, printed, or plotted.
4-2.3
Totalizers. Provide a 8-digit minimum totalizer. Provide a lock to inhibit the
reset function of reset type totalizers.
Whenever practical, record the data on a computer disk, tape, or other
permanent data storage device and use a computer program to add up the totals.
4-2.4
Indicators. Dedicated indicators are commonly used with pneumatic and
analog type of control systems.
Do not specify a dedicated indicator except for critical items when using
digital type control systems. Obtain non-critical information from a control station read-
out or from a monitor.
4-2.5
Status Lights. Do not specify a dedicated status light except for critical
items. When dedicated status lights are required, use neon rather than incandescent
lights as much as practical. Neon lights have lo wer power consumption and longer life.
Use "Push to Test" indicating/status lights to ensure lights are functioning properly.
4-5
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