Rockwell Automation Allen-Bradley 1734-IB8S, User Manual

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98 Rockwell Automation Publication 1734-UM013J-EN-P - July 2014
Chapter 5 Configure the Module in a GuardLogix Controller System
Configure Tachometer Operation
You can only configure the module for tachometer operation if your Module
Definition includes Output Data for Safety-Tachometer.
Follow these steps to define how the module operates in Tachometer mode.
1. From the Module Properties dialog box, click the Tachometer
Configuration tab.
2. Turn Dual Low Detection ON or OFF for each channel pair.
To increase the diagnostic coverage of your speed sensing loop, you need to
determine whether the two tachometer sensors you are using to sense
speed are shorted together. That is, you need to be able to detect a
channel-to-channel fault. One method is to implement two tachometer
sensors so that, during normal operation, their pulse trains are never low at
the same time. When Dual Low Detection is ON, the module detects this
condition as a fault, indicating that the two sensors are shorted together.
To use this feature, you must use Channels 0 and 1 together, and Channels
2 and 3 together. Channels 0 and 1 have the same setting and channels 2
and 3 have the same setting.