Table Of Contents

Thresholds

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    Last Modified: May 15, 2018

    The Safety Editor allows you to set four current thresholds for each analog input configuration. The User Program applies the threshold values to every channel in the configuration.

    Figure 1. Thresholds

    Current thresholds define five regions that describe the state of the input. The module FPGA converts the current region for a channel into a Boolean value that can be read by the User Program. You can use the Boolean values for a current region as transition conditions in the state machine diagram.

    Figure 2. Current Regions

    Refer to the following guidelines when configuring thresholds:

    • The four thresholds must be in a consecutive, increasing order. Low must have a larger value than low low, high must have a larger value than low, and high high must have a larger value than high.
    • To ensure the module FPGA returns a low low region for a channel, set the low low threshold high enough to filter out inaccuracy and noise.
    • The hysteresis ranges of two thresholds must not overlap. If you set the hysteresis range to 0.100 mA, the difference between any two thresholds must be >0.200 mA.
    • If your system requires fewer than five configured current regions, you can conceal unnecessary regions, but the configured regions must be adjacent. For instance, you can configure low, normal, and high current regions, but not low, normal, and high high current regions.
    • Set the high high and/or low low thresholds to their extreme values to conceal the outermost current regions.
    • When concealing an outermost current region, use Boolean OR statements in transition conditions. For instance, if you don't want to use the high high current region, transitions that trigger on high should read AIn.H or AIn.HH.

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