WEBVTT

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Ground Truth, for technicians.

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Where the signals live,
and how to troubleshoot.

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Inside CP-101:

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a MicroLogix controller, two level
trip amplifiers, and relays K1 to K5.

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The input and output lights and
every relay follow the live logic.

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K1 and K2 carry the pump permissives.

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K5 is the LY-V110 trip relay,
energized when healthy.

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The two output fuse carriers for the horn
and the common alarm were found open.

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The external trip from X130 arrives as a
DC signal, through a solid-state relay,

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SSR1.

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On the I/O tab, every
signal has its terminal,

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its live value in the controller and
in the field, and a force selector.

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Now the important one.

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These trip inputs only trip
when they are energized.

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We open the wire to the LY-X130
input, and then X130 sends a trip.

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Nothing happens.

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The pump keeps running.

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To the controller, a broken wire looks
exactly like a healthy, quiet input.

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Restore the wire, and the trip goes through:

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the pump trip latches, and the pump stops.

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The event log lists every
change in scan order:

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the input first, then the
latches and outputs it caused.

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Start there when something trips.

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An open wire on a trip input gives no trip.

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Prove every trip, end to end.