647C 3. Functionality
27
3.7.5 Trip Limit Supervision
MGC 647C V3.0
CH1 CH2 CH3 CH4
ACT.FLOW 0.000 1.750 1.400 0.000
UNIT SCCM SCCM SLM SLM
MIN.LIMIT 3.000 0.750 0.000 0.000
MAX.LIMIT 4.000 0.250 1.400 1.450
SUPERVIS. LIMIT
BAND SLEEP SLEEP
STATUS OFF ON ON ON
00 ERRORS FLOW ON INPUT DIRECT
Figure 18
There are three modes to supervise the process gas flows.
- SLEEP mode
- LIMIT mode
- BAND mode
In SLEEP mode no supervision is performed. In LIMIT mode the actual flow is supervised to
remain between the trip limits. If the actual flow exceeds the high limit or falls below the low limit an
error will be generated. The limits are considered as absolute values. The BAND mode is similar to
LIMIT mode, but the limits are considered as deviation to the setpoint. The low limit represents
negative deviation.
The supervision becomes active 1 second after the selection of a mode.
Two relays are driven by each channel, if the Relay Option is used. The logic of the relays depends
on the actual Supervision Mode:
- SLEEP mode
In this mode relay 1 represents the status of the channels’s valve. Relay 2 is idle.
- BAND mode
In this mode relay 1 also represents the status of the channel’s valve. Relay 2, however, will
become active if the actual flow is outside of the defined band.
- LIMIT mode
If the actual flow is below low limit, relay 1 will become active, and if it is above high limit
relay 2 will become active.
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