User`s guide

318
Chapter 7 Tutorial
Multifunction Module
• You can control when the totalizer actually records counts by
providing a gate signal (G and terminals on the module). A TTL
high signal applied to the “G” terminal enables counting and a low
signal disables counting. A TTL low signal applied to the “ ”
terminal enables counting and a high signal disables counting. The
totalizer only counts when both terminals are enabled. You can use
either the G terminal, the terminal, or both. When a gate is not
connected, the gate terminal floats to the enabled state, effectively
creating a “gate always” condition.
Totalizer Errors
• Noise on the totalizer input can be a problem, especially on signals
with a slow rise time. This noise can create a false indication of a
threshold crossing. For more information on cabling noise, see page
257.
• Contact bounce on external switches can create false counts. All
mechanical switches bounce when they open and close. Use an
external capacitor to filter the contact bounce.
G
G
G
Input Signal
(Rising Edge)
Gate Signal
(High True)
Totalizer Input
Add to Total
Limit Switch
+5 V
Switch
Closed
Totalizer
Noise caused by bounce
creates a false count
34970A Refresh UG.book Page 318 Wednesday, February 17, 2010 12:34 PM