User manual

Model: 2100 &2300 Series
2100UM22.DOC Rev: 2.2
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for the appropriate relay indicates the alarm condition. The relay is de-energized (with no delay)
when the level falls below the low control point. Selecting low action will energize the relay when
the level falls below the low control point for at least the time delay period. The relay is de-
energized (with no delay) when the level rises above the high control point.
4. FAILSAFE
. Failsafe typically means that the relay is normally (when not in an alarm condition)
held in an energized state. In an alarm condition, the relay is de-energized i.e. identical to when
the instrument power is shut off. The rationale is that the alarm condition should match the
Power Fail condition.
5. RELAY DELAY
. Minimum time in seconds for an alarm to exist before the corresponding relay
is set to its alarm state. The relay alarm state depends on the Relay Action and Failsafe
settings.
4.3.3 RELAY SETTINGS SELECTION
1. Identify the positive action required in the control application such as turning on a pump,
opening a valve, or sounding an alarm. Note: the time delay is applied to the start of the
positive action; also, the corresponding LED is turned on to indicate the positive action.
2. Identify if Fail Safe condition is required in an alarm condition. For control applications (relay
used to control pump etc.), the positive action may also be viewed as the opposite state
desired in the event of a power or instrument failure. For alarm applications (relay used to
indicate an abnormal condition such as a high tank level), the positive action may be the
same state desired in the event of a power or instrument failure.
3. Identify the type of relay action required: if the positive action is required when the level
exceeds the high control point then select High Action for the relay. If the positive action is
required when the level falls below the low control point then select Low Action.
4. Identify the relay contacts to use (either Normally Open or Normally Closed). The contacts
used are dictated by the failsafe setting and if the positive action requires the application of
power or removal of power to the controlled device.
The following table summarizes the settings for all possible requirements:
# DESIRED CONTACT CONDITIONS DO THIS
BELOW
LOW SETPOINT
ABOVE
HIGH SETPOINT
INSTRUM. Or
PWR FAILURE
FAILSAFE
SETTING
RELAY
ACTION
USE
CONTACTS
1 Open Closed (PA) Open No High Acting NO
2 Open Closed (PA) Closed Yes High Acting NC
3 Closed (PA) Open Open No Low Acting NO
4 Closed (PA) Open Closed Yes Low Acting NC
5 Open (PA) Closed Closed No Low Acting NO
6 Open (PA) Closed Open Yes Low Acting NC
7 Closed Open (PA) Closed No High Acting NO
8 Closed Open (PA) Open Yes High Acting NC
 (PA) = positive action desired such as turning on a pump.