HARDWARE MANUAL Document reference MAMPS-HW/E
VM600 machinery protection system (MPS) Edition 18 - March 2022
5-12
System self-checks
AMC8 / IOC8T CARD PAIR
In practice, it can take up to 350 ms (“confirmation time” + “response time”) after an input
signal goes outside the configured OK levels before it is confirmed and acted upon in a
VM600 system as an OK System failure.
When there is an OK System failure on an AMC8 card:
• For the channel in question, the corresponding status indicator (LED) on the panel of the
card blinks green and an OK level alarm (corresponding to the individual
Global Channel OK bit) is signalled.
For example, this can be used to switch a relay on the IOC4T or RLC16 card.
NOTE: Any alarms (A+, D+ and so on) associated with the corresponding monitoring
channel are not inhibited, but remain active.
For an AMC8/IOC8T card air, the monitoring performed by the OK system depends on the
type of sensor input, as follows:
• Thermocouple (TC) devices:
No line-fault detection (open-circuit or short-circuit conditions).
• Resistance temperature detector (RTD) devices:
Line-fault detection of open-circuit and short-circuit conditions.
• DC signals (current or voltage):
Line-fault detection of open-circuit and short-circuit conditions.
NOTE: When a measurement channel of an AMC8/IOC8T card pair is configured for
operation with thermocouple (TC) devices, the sensor input does not support
line-fault detection of conditions such as an open-circuit.
When a thermocouple (TC) device is connected to a measurement channel of an
AMC8/IOC8T card pair and one of the connections becomes open-circuit (that is, the
thermocouple is effectively disconnected), a temperature measurement deviation will occur
until either the minimum or maximum measurable temperature is reached and any configured
alarms (alert and/or danger levels) are activated.
In practice, such a temperature measurement deviation occurs quite slowly with reported
temperature measurements of the order of approximately 10°C (18°F) per second.
5.9.2 Built-in self test (BIST)
The AMC8 and IOC8T feature built-in self test (BIST) circuitry which provides information
about the operational state of the system. There are basically three types:
1- Global Board BIST
This tests the IOC as a whole and includes a logic watchdog.
2- Channel BIST
This checks each channel to establish whether:
• The shield (S) terminal is incorrectly connected to the sensor (S) terminal
• The linear regulator voltage is correct
• The DC-DC output voltage is correct.
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