8
.
5
T
endency recognition
T
he function of the tendency recognition is to recognize a de
fi
ned
change within a certain time period and to transfer this information to a
relay output
.
T
he information for tendency recognition is generated out of the
measured value change per time unit
.
T
he output variable is always
the measured value in percent
.
T
he function can be con
fi
gured for
rising and falling tendency
.
T
he actual measured value is determined
and summed with a sample rate of a second
.
A
fter the max
.
reaction
time
,
the average value is generated out of this sum
.
T
he real
measured value change results then of the newly calculated average
value less the previously calculated average value
.
I
f this di
ff
erence
exceeds the de
fi
ned percentage value
,
the tendency recognition
responds and the relay deenergises
.
N
ote
:
T
he activation and con
fi
guration of the tendency recognition requires
PACT
ware with the suitable
DTM
.
S
etting parameters via the
integrated indicating and adjustment unit is not possible
.
l
M
easured value change higher
:
M
easured value change per
time unit
,
at which the tendency recognition should respond
l
M
ax
.
reaction time
:
T
ime after which a new measured value
generation is carried out and the measured value change is
recalculated
l
H
ysteresis
:
is automatically always
10
%
of the value of
"
M
easured value change larger than
"
l
R
eaction in case of failure
:
I
n case of a failure
,
the relay goes
into the de
fi
ned condition
N
ote
:
A
fter switching on or a failure
,
always two complete cycles must be
executed until a measured value di
ff
erence can be calculated and a
tendency can be outputted
.
T
he level in a basin should be monitored on rising tendency
.
I
f the rise
is higher than
25
%
per minute
,
an additional emptying pumpt should
be switched on
.
T
he max
.
reaction time should be one minute
.
I
n case
of a probable failure
,
the pump should be switched o
ff
.
S
elect in the
DTM
navigation section the menu items
"
M
eas
.
loop
-
O
utputs
-
R
elay
"
.
l
E
.
g
.
set for relay
1
the mode
"
R
ising tendency
"
l
S
elect under
"
R
eaction in case of failure
"
the option
"
S
witching
condition o
ff
"
l
E
nter the following values into the parameter
fi
elds
:
-
M
easured value more than
25
%
/
min
.
-
M
ax
.
reaction time
1
min
.
F
unctional principle
P
rinciple of operation
P
arameter
E
xample
S
et up
VEGAMET
625
•
D
ouble channel
HART
signal conditioning instrument
49
8
A
pplication examples
28970
-
EN
-
110801