Endress+Hauser silometer FMC 671 Z - Level Limit Switching

8.2 Level limit switching
Operating mode 2 is used for level limit detection in fluids or bulk solids. To serve as a
limit signal transmitter,
• a capacitance probe for liquids or bulk solids or
• a vibration limit switch, Liquiphant for liquids or Soliphant for bulk solids,
can be connected at channel 2.
Relay settingsIn operating mode 2, the relay switch points are in Hz. On fault condition, the relays
de-energise, fail-safe mode is set at V1H1/V1H6 (default = maximum).
• Enter 2 at V1H4 to switch relay 1 to channel 2
• For capacitive probes, the result of the calibration at V8H5 is written in Hz into
field V1H5
• The switching point, and hysteresis for Relais 1 are entered in Hz at
V1H0/V1H2 (take values from V1H5/V1H7).
Capacitance probeFig. 8.3 shows the set up for limit switching with capacitance probes. The probe can be
built in horizontally or vertically. The relay trips as soon as the product exceeds the
calibration point set at V8H6. The entry at V8H6 provides build-up compensation by
shifting the switch point for vertical probes by the amount indicated in Table 8.1. The
default value 1 Hz = approx. 5 pF. A higher value decreases the sensitivity.
level
limit
detection
switching point
hysteresis
min. / max. fail-safe mode
switching delay
frequency
2
Limit 1 or 2
relay
relay
BA063E42
Fig. 8.2:
Schematic diagram,
limit level switching
Relay 1 must be assigned to
channel 2 at V1H4
BA063E43
Minimum
fail-safe mode
Maximum
fail-safe mode
Channel 2
or
Relays 1
and 2
non-Ex
Ex
Fig. 8.3:
Schematic diagram,
limit level switching with
capacitance probes
➀ Minimum fail-safe
➁ Maximum fail-safe
Silometer FMC 671 Z/676 Z Chapter 8: Other Applications
43