Miscellaneous
totalizer and samplers : - refer to Application Pump Totalizer and OCM . Relays
are normally de-energized, contact closure is
approximately 200 mSec duration.
scanner : - this function is specific to relay 5 and the DLD mode of operation.
The transducer hot is wired to the common terminal of the relay
so that when switched, the transceiver may alternately access
transducer #1and #2.
Refer to Applications \ Differential Level Application.
Setpoint - ON / OFF
If the ON setpoint is higher than the OFF setpoint, the relay operates as :
» high alarm
» pump down control
» high differential alarm
If the ON setpoint is lower than the OFF setpoint, the relay operates as :
» low alarm
» pump up control
» low differential alarm
The ON and OFF setpoints can not be the same on an individual relay but may be
common to other relays. The dead band or hysteresis is the difference between the
ON and OFF setpoints. For in and out of bounds level alarms, the hysteresis is set
±2 % of span from either boundary.
The setpoints for alarm functions 1 - 4 and pump functions 8 - 10 are always entered
in the P-1 units of measurement selected (but not %). The setpoints are measured
from the bottom up, referenced to zero or empty except for the differential functions,
4 and 10. There the setpoints represent the absolute differential between levels,
regardless of the level with respect to zero.
Relay status - non run modes
When the fail-safe timer expires, pump control relays respond as previously
described. However, alarm relays will respond in the following manner.
Upon entering the program mode, all pump control relays will be turned OFF. Alarm
relays will hold their prior status, but will respond to measurements take when "MEAS"
is pressed.
FAIL-SAFE MODE RELAY STATUS
P-74 high alarm low alarm
fail-safe high on off
fail-safe low off on
fail-safe hold hold hold
PL-443 5 – 7
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