Spectrum Controls 1756sc-CTR8 - Manual (Page 54)

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ControlLogix ™ Counter Module
Meter Proving
The 1756sc-CTR8 module provides a feature that allows the user to
perform meter proving functions. A typical meter proving application
would include two detector sensors that are located a fixed distance from
each other within a section of pipe used specifically for meter proving.
The operation does not disrupt the in situ flowmeter’s operation.
Detector #1 Detector #2
Displacer
Utilizing the external gate enable to start and stop count functions enables
the user to count pulses as fast as 65kHz to an accuracy of 1 count.
Here is an example wave form representing the start and stop transitions
on the external gate enable, and the associated pulses that the module
would accumulate: [Storage mode 3, store, reset, wait, start]
Flow Meter Input
External Channel Enable
1 2 3 4 NA
Given the above wave form, the module will begin counting the first
positive going input pulse after the external enable input goes low. The
module will accumulate 4 counts in the channel count register and stop
when the external enable input goes high.