4.4 Relays
Operating modes The Prolevel FMC 661 has five independent relays with potential-free changeover
contacts. Relays 1a, 1b, 2a and 2b are limit relays, relay 3 is an alarm relay which always
de-energises on fault condition. Relays 1a and 1b are set together, as are 2a and 2b.
Five parameters set the limit relays, Table 4.1 summarises their function:
Relay on alarm The limit relays respond to an alarm according to the entry at V1H3/V1H8 (0 =
de-energise, 1 = as Table 4.2). When the relays are assigned to the external limit switch
(see Chapter 5) they always de-energises on alarm.
r u a r u a r u a
3
51 52 53 51 52 53
51 52 53
11 12 13
21 22 23
31 32 33
41 42 43
11 12 13
21 22 23
31 32 33
41 42 43
11 12 13
21 22 23
31 32 33
41 42 43
1a
1b
2a
2b
r u a r u a
r u a
power failure: de-energised
Limit relays
1a, 1b , 2a, 2b
yellow LEDs
Alarm relay 3
red LED
faultnormal operation
BA142_40
normal operation
power failure: de-energised
Fig. 4.14:
Relay LEDs as a function of relay
status:
limit relay: lit, energised
out, de-energised
alarm relay (default setting):
lit, de-energised
out, energised
Parameter Matrix position for
relays
Entry/Function
1a, 1b 2a, 2b
Switch point V1H0 V1H5 Relay switch point in calibration/linearisation units
Fail-safe mode V1H1 V1H6 0: minimum fail-safe mode: — the relay
de-energises when the level drops below the
switch point, see Fig. 4.15.
1: maximum fail-safe mode — the relay
de-energises when the level rises above the
switch point, see Fig 4.16.
Hysteresis V1H2 V1H7 Range at end of which the relay energises again
Relay on alarm V1H3 V1H8 0: de-energised
1: as analogue output: see Table 4.2.
Relay assignment V1H4 V1H9 1: channel 1
2: channel 2
Table 4.1:
Parameters for setting limit relays
Setting at V0H7 Minimum fail-safe mode Maximum fail-safe mode
0 = -10% (≤ -2 mA) Relay de-energises Relay energises
1 = +110% (≥ +22 mA) Relay energises Relay de-energises
Table 4.2:
Relay response on fault
condition when V1H3/V1H8 = 1.
Chapter 4: Level Measurement Prolevel FMC 661
32 Endress+Hauser
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