KROHNE MFC 010 C Converter - Manual (Page 80)

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MFC010 Interface Manual
8.8 Using the Internal Process Control Mechanism
The internal process control system permits t he us er t o l imit t he m easurement w hen t he pr ocess
conditions are outside of the prescribed limits as defined in the Internal Process Control settings.
The p rocess c onditions under w hich t he c ontrol m echanism i s em ployed ar e def ined in the holding
registers ( s ee s ection 7.5 on page 49 ). H olding r egister N o.1010 determines the source of t he
controlling variable, i.e. the process t emperature or t he pr ocess dens ity. T he c ontents of H olding
registers 3051 and 3053 determine the minimum and m aximum limits of the controlling variable, outside
of which the process control mechanism will be applied.
When applied, the process control mechanism will perform one of three functions, defined by the setting
of Holding register no 1009.
Holding Register 1009 = 1 : The Internal Process control mechanism is disabled
Holding Register 1009 = 2 : The Flow readings are forced to zero
Holding Register 1009 = 3 : The Flow readings are forced to zero and all of the totalisers are reset.
When the Internal Process control mechanism is active, i.e. the defined process condition is beyond the
set limits, the “Process control active” bit in the Exception Status message (see section 6.7 on page 29)
will be set. This status bit is also accessible in Discrete Input register no. 1009 (see section 7.3 on page
41).
8.9 Custody Transfer Applications
To provide added security for use in C ustody t ransfer appl ications t he MFC010 has been des igned t o
include a C ustody T ransfer P assword. T his pas sword will pr event any c hanges t o t hose configuration
variables (Holding registers) that have any effect on t he measurement result. T he Custody password is
activated by writing a 16-bit password value of the user’s choice to the Custody transfer password register
(Holding Register No. 1003). When the Custody Transfer protection is activated it will be indicated in the
Binary Input register Number 1003. Those configuration variables that are write protected by the Custody
Transfer Password are indicated with the symbol
CT
in the Register definitions. The Custody transfer
protection also extends to the resetting of certain Error flags, see section 9 for details.
Writing an incorrect value to a password register on three consecutive occasions will result in a 10 minute
“lockout” of that register, i.e. subsequent writes to that register, whether with the correct password or not,
will be r ejected with an “ Illegal Function” error response. See Section 5.6 on page 22 for details of the
error response telegram formats.