Cut Sheet

156
www.ssac.com • 800-843-8848 • fax: [phone]
Selecting a Timer’s Function
Selecting one of the ve most common timing functions can be as easy as answering three questions on the chart below. If you have trouble answering
these questions, try drawing a connection diagram that shows how the timer and load are connected. Time diagrams and written descriptions of the
ve most popular functions, plus other common functions. Instantaneous contacts, accumulation, pause timing functions, and ashing LED’s are
included in some units to expand the versatility of the timer. These expanded operations are explained on the product’s catalog page. Time diagrams
are used on these pages along with text and international symbols for functions.
Function Selection Guide
Selection Questions
1) The timing starts when the
initiate (starting) contacts are:
A) Closed B) Opened
2) What is the status of the output
(or load) during timing:
A) On B) Off C) On/Off
3) Will the load de-energize
(or remain de-energized)
if the initiate (starting) contacts
are opened during timing:
A) Yes B) No
THE FIVE MOST USED FUNCTIONS
Understanding Time Diagrams
Time diagrams are used to show the relative operation of switches,
controls, and loads as time progresses. Time begins at the rst vertical
boundary. There may be a line indicating the start of the operation or it
may just begin with the transition of the device that starts the operation.
Each row in the time diagram represents a separate component.
These rows will be labeled with the name of the device or its terminal
connection numbers. In a bistable or digital system, the switches,
controls, or loads can only be ON or OFF. The time lines are drawn
to represent these two possible conditions. Vertical lines are used to
dene important starting or ending points in the operation.
The example to the right is the most common type of time diagram
in use in North America. It shows the energizing of loads, and the
closing of switches and contacts by an ascending vertical transition of
the time line. Opening switches or contacts or de-energizing loads are
represented by descending vertical transitions.
TIME DIAGRAM
Example:
Input Applied
Off
Output Energized
(Normally De-energized
Open)
Initiate Closed
Switch Open
R = Reset TD = Time Delay S1 = Initiate Switch
Delay-on-Break (Release)
Undened time t = Incomplete Time Delay
Appendix A - Timer Functions