Basic Information On Relay Functions; Event Monitoring; Limit Indicator - wtw DIQ/S 182-MOD System Operating Manual

System 182
ba75504e07 04/2012
6.3

Basic information on relay functions

In this chapter, you will find general basic information concerning the
following relay functions:
 Event monitoring (see section 6.3.1)
 Limit indicator (see section 6.3.2)
 Proportional output (see section 6.3.3)

6.3.1 Event monitoring

When using a relay for event monitoring, a relay action (Open, Close)
occurs when the monitored event takes place.
This function is suitable, e.g. for the monitoring of errors in the system.
If an event takes place, the relay works as an alarm contact.
Note
For monitoring functions, use the relay preferably as an opener. In the
case of an error, the relay opens. As a result, the monitoring function
operates even if, e.g. the supply voltage fails.

6.3.2 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 6-6).
 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 6-6).
Note
If the simple monitoring function (Open, Close) with one or two relays
is not sufficient, use proportional output (see section 6.3.3).
Relay outputs
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