LD Language Elements
SR2MAN01 11/2007 129
Analog Comparators
Description The Analog Comparators function block is used to:
z Compare a measured analog value with an internal reference value.
z Compare two measured analog values.
z Compare two measured analog values with hysteresis parameter.
The result of this comparison is used in the form of a contact.
Analog automation functions can be used for smart relays with a real time clock and
DC power supply, and with mixed DISCR/Analog inputs.
The following indicate the existence of mixed Discrete/Analog inputs:
z The existence of inputs numbered from IB to IG (maximum configuration). These
inputs are used to receive analog signals from 0.0 V to 9.9 V inclusively.
z The presence of the Analog Comparators function in the toolbar of the
programming software.
These smart relays have 16 Analog Comparators function blocks, numbered from
1 to 9 then from A to G.
Use as a Contact The contact shows the position of a measured analog value in relation to a reference
value or to another measured value.
It may be used as many times as necessary in the program. It may be used
according to 2 modes: normally open or normally closed, described below.
Normally open mode:
Symbol of the normally open contact associated with a, Analog Comparator:
The contact is conducting when the comparison condition is verified.
Normally closed mode:
Symbol of the normally closed contact associated with an analog comparator:
The contact is conducting when the condition is not verified.
A-
a-