
Publication 1794-6.5.11 - November 1997
Overview of the Frequency Input Module
1
-5
Output Capabilities
The 1794-IJ2 module has 2 assignable outputs. These outputs are
designed for applications that require fast response. The outputs:
•
are current sourcing at 10-31.2V dc (1A maximum per output)
•
are electrically fused/current limited to 3A
•
can be assigned to the associated input channel with user-selectable
frequency and acceleration values
•
are isolated — this lets you use two separate external power supplies
if desired (one for output 0 and one for output 1)
Implementing Application Features
You can use the module to implement programmable application features
that are usually initiated by your PLC processor. This frees the PLC
processor to do other tasks and helps increase the overall throughput of
your PLC system.
How Frequency is
Calculated
The following paragraphs detail operation of the frequency input module
algorithm and its modifying parameters.
Frequency Calculation
Frequency is determined by a general algorithm which can be modified by
user defined parameters. In its simplest form, the algorithm employs the
user defined Minimum Sampling Time to set a window in which to count
pulses to determine the frequency. At least two pulses are required within
the sample window. Frequency is determined by storing the time the first
pulse occurred and then continually storing and updating the time of
subsequent pulses, along with the number of pulses encountered. When
the window expires, the frequency is calculated and the procedure repeats.
The sequence and formula for determining frequency are shown below.
This feature
Is used in these modes
To
Alarm is ON when
frequency alarm
frequency alarm selected
activate alarm when calculated or scaled
frequency is higher than user-specified
frequency value.
frequency
>
user-specified value
acceleration alarm
acceleration alarm
selected
activate acceleration alarm when acceleration is
greater than user-specified acceleration value.
acceleration
>
user-specified value
scaling
% full scale and
acceleration
multiply and/or divide frequency by scalar
frequency
>
user-specified scaled
frequency value
Содержание FLEX I/O 1794-IJ2
Страница 1: ...User Manual FLEX I O Frequency Input Module Cat No 1794 IJ2 Allen Bradley Allen Bradley Replacements ...
Страница 6: ...Publication 1794 6 5 11 November 1997 4 Using This Manual ...
Страница 19: ...Publication 1794 6 5 11 November 1997 1 10 Overview of the Frequency Input Module Allen Bradley Replacements ...
Страница 38: ...Publication 1794 6 5 11 November 1997 3 6 Programming Your Frequency Input Module ...
Страница 67: ...Publication 1794 6 5 11 November 1997 6 4 Troubleshoot the Frequency Input Module Allen Bradley Replacements ...