Meggitt VM600 Hardware Manual

VM600 MPS hardware manual (standard version) MAMPS-HW/E 4 - 23
Edition 17 - February 2018
System self-checks
MPC4 / IOC4T CARD PAIR
4.7 System self-checks
4.7.1 OK system checking
The OK System monitors the input signal from the sensor in order to verify if the sensor is
connected and operating normally. To do this, the DC signal level is compared against two
user-configurable OK levels: a minimum normal level and a maximum normal level. This is
shown in Figure 4-10.
Any problem with the transducer and/or signal conditioner or connecting cable that causes
the signal to deviate beyond these OK levels will cause an individual alarm for the input
channel (corresponding to the individual Sensor OK bit) and a common alarm for the MPC4
card (corresponding to the common Sensor OK bit).
As shown in Figure 4-10:
• The “confirmation time” is a fixed firmware time delay used so that only an input signal
that is outside the configured OK levels for a time period greater than 250 ms is detected
as an OK system failure. This is used to ensure that noise (“spikes”) on the DC signal
level are not accidentally recognised as failures.
• The “response time” is the maximum time delay from the time that an OK system failure
is detected until the corresponding alarms are set (Sensor OK bit for the input channel
and Common Sensor OK bit alarm for the MPC4 card). The actual time delay depends
on the processor load of the card but is less than 100 ms.
NOTE: The behaviour of the OK system checking is the same above and below the
configured OK levels.
Confirmation
time:
Response
time:
Figure 4-10: Maximum and minimum signal levels allowed by the OK System
DC signal
level
Normal
tolerance
Voltage sensor connection short-circuit or
current sensor connection open-circuit
Time
Sensor
OK
Time
Voltage sensor connection open-circuit or
current sensor connection short-circuit
100 ms<250 ms
Recovery time:
100 ms for MPC4 versions 070 or earlier.
10 s for MPC4 versions 071 or later.
(Except for MPC4 version 072, a “custom”
version, which is 60 s.)
Grounded
Open
Sensor OK
Min.
(Lower OK Level)
Max.
(Upper OK Level)

Meggitt VM600 Specifications

General

Brand	Meggitt
Model	VM600
Category	Measuring Instruments
Language	English