Xylem DIQ/S 281, Operating Manual

Page: 97 / 148

DIQ/S 281 Outputs
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03/2023
6.2 Basic information on relay functions
This chapter describes general basic information concerning the following relay
functions:
 Monitoring (see section 6.2.1)
 Limit indicator (see section 6.2.2)
 Proportional output (see section 6.2.3)
6.2.1 Monitoring
When using a relay for monitoring, a relay action (
Open
,
Close
) occurs when
certain states occur. This function is suitable, for example, for the monitoring of
errors in the system.
6.2.2 Limit indicator
With a limit indicator, a relay switches when a specified limiting value is
exceeded or undercut.
Limit indicators can be used in the following way:
 Monitoring a limiting value using a relay:
when a limiting value (upper or lower limiting value) is exceeded or undercut,
a relay switches. The
Open
or
Close
relay actions are possible in each case
(see page 98).
 Monitoring two limiting values using two relays:
If the upper limiting value is exceeded or undercut, a relay switches, and if
the lower limiting value is exceeded or undercut, another relay switches. The
Open
or
Close
relay actions are possible in each case (see page 98).
For monitoring functions, use the relay preferably as normally
closed (see section 6.6.1). In the case of an error, the relay opens.
As a result, the monitoring function operates even if, for instance,
the supply voltage fails.
If the simple monitoring function (
Open
,
Close
) with one or two
relays is not sufficient, use proportional output (see section 6.2.3).