ProSoft Technology MVI56-AFC - Manual (Page 58)

Meter Proving MVI56-AFC ♦ ControlLogix Platform
User Manual Liquid and Gas Flow Computer
Page 58 of 316 ProSoft Technology, Inc.
February 25, 2011
Missed Switch
It is possible that the tripping of the second switch to end a run is not seen by
the PLC (due to a broken wire or poorly lubricated switch), leaving the AFC and
the physical prover in inconsistent states. You may recover from this condition
with the Run Cancel signal, which clears any active run and resets the AFC to be
ready to start a new run. Data from any bad run will also be deleted by the Run
Cancel.
Proving Controls
These bits supply parameter information to the Enable prove and Accept prove
signals (register 65308 bits 1 and 2 respectively). Control bits 0 through 7
parameterize the Enable and bits 8 through 15 parameterize the Accept. Controls
are latched into the results database upon receipt of a signal. Changes thereafter
have no effect on the state of these control bits.
Proving Signals
A prover signal instructs the AFC to immediately perform a particular function
once. A signal bit is latched by the process issuing the signal (for example, the
PLC) and is unlatched by the AFC when the function has been performed. Prover
signals are discharged upon the next proving scan, before which several Modbus
transactions may be completed. Modbus transactions to read the status of these
signal bits may, therefore, show uncleared bits for functions that have already
been scheduled but not discharged yet.
Prover Sequencing
This parameter reports the state of the proving hardware, making it available to
the prove-management software for display of prove status and possible control
of the prove. The prove-management feature of AFC Manager uses it only for
display. This value usually comes from the proving hardware integrated into the
PLC platform, therefore it is normally supplied by the PLC.