Meggitt VM600 Hardware Manual

5 - 10 VM600 MPS hardware manual (standard version) MAMPS-HW/E
Edition 17 - February 2018
Alarm monitoring
AMC8 / IOC8T CARD PAIR
5.7.4 Channel inhibit function
The channel inhibit function allows individual AMC8 channels to be temporarily bypassed,
that is, it temporarily inhibits the protection offered by any associated relays.
The channel inhibit function is intended to allow a component in a measurement system
front-end, such as a sensor/transducer or signal conditioner, to be replaced for an individual
channel while the other machinery monitoring channels and functions continue to operate as
normal.
This allows the machinery being monitored to continue to operate (if the protection offered by
the other machinery monitoring channels and functions is adequate). It also allows any
control system using the relays to avoid false trips during such maintenance activity.
When the channel inhibit function is activated for an AMC8 channel:
• The channel continues its processing as per its configuration but inhibits the protection
offered by any associated relays.
This allows the effect of any changes to the measurement system front-end to be
observed. In this way, it can also be ensured that there are no ongoing alarm conditions
before the de-activation of the channel inhibit.
• Any DC output functionality associated with the channel continues, if enabled.
• The following flags (bits) for the channel processing are forced to a known state:
• The error bit (Err), OK system check (SOK), alarm (A+, A) and danger (D+, D)
flags are all forced to a normal state (which is false, that is =0).
The sensor bypassed (SBP) flag and the global channel OK fail flags are also set
active.
NOTE: The VM600 MPS1 and VM600 MPS2 software packages use the SBP (sensor
bypassed) flag to refer to the channel inhibit function.
• Any processing channels that depend on the channel are automatically bypassed.
• The channel’s status indicator (LED) on the panel of the AMC8 card slowly blinks green
for the duration of the channel inhibit (approximately once per second).
When the channel inhibit function is de-activated for an AMC8 channel, the card:
• Waits 12 seconds for signal stabilisation (total recovery time).
• Resets (clears) any latched alarms.
• Stops forcing the flags for the channel processing to a normal state, so that the true
status of the machinery monitoring system is returned again. The sensor bypassed
(SBP) flag is also set inactive.
NOTE: When an AMC8 card is configured (using the VM600 MPS software), the channel
inhibit function is automatically de-activated for any channels where it is active.
The status of the channel inhibit function for the individual channels of an AMC8 card can be
used as an input to a basic function (see 5.7.2 Logical combinations of alarms).
Se also 5.7.3 Danger Bypass function and 10.6 Channel inhibit function.

Meggitt VM600 Specifications

General

Brand	Meggitt
Model	VM600
Category	Measuring Instruments
Language	English