Publication 1794-6.5.11 - November 1997
1-8
Overview of the Frequency Input Module
Direction Detection
Direction detection is accomplished by using the Frequency input, Gate
input, and two sensors. The module expects to see a Low to High
transition on the Frequency input, followed by a Low to High transition
on the Gate input. This assumes both input polarity select bits are the
same selection.
This corresponds to Clockwise rotation (see figure). If a Low to High
transition occurs on the Gate input, followed by one on the Frequency
input, the rotation is CounterClockwise.
Missing Pulse Multiplier
Frequency Reported at
First Pulse in Extended Time =
T2 - T1
2 - 1
Minimum Sampling Time
Frequency Input
Pulses
first pulse in window,
T1 time stored
first pulse in an extended window,
T2 time stored
extended windows added one at time, until
pulse occurs or multiplied windows exceeded
Missing Pulse Alarm Would be Reported After Last Window, If No Pulse Occurs
possible extended window
2 = pulses counted
Sensor 0
Sensor 1
Clockwise Rotation
Frequency Input
IJ2 Module
Gate Input
M
2 x M
Sensor 0 (F)
Sensor 1 (G)
Clockwise
Rotation
Counter
Clockwise
Rotation
Sensor 0 (F)
Sensor 1 (G)
Direction Detection - Principle of Operation