Vega VEGAMET 391, Руководство по эксплуатации, Страница: 46 / 68

S
witched
-
on time "
. I
f a considerable di
ff
erence between the pumps is
determined
,
it means the capacity of one of the pumps must have
fallen considerably
. T
his information can be consulted for diagnosis
and service
,
e
.
g
.
to recognize plugged
-
up
fi
lters or worn out bearings
.
S
ince in this case all pumps are operated alternately in the same area
,
their switch
-
on and switch
-
o
ff
points should theoretically be set the
same
. H
owever
,
this would cause all relays to always switch on or o
ff
together
. T
o achieve suitable switching characteristics
,
one relay must
be assigned the desired switching points
;
the other relays are
assigned switching points that are never reached in normal operation
,
e
.
g
.
110
%
and
-
10
%
.
N ote :
T
he index of the lastly switched on relay is not saved in case of voltage
loss
,
this means that adter switching on the signal conditioning
instrument
,
always the relay with the lowest index starts
.
8 . 4 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 more than "
l
R
eaction in case of failure
: I
n case of a failure
,
the relay goes
into the de
fi
ned condition
F unctional principle
P rinciple of operation
P arameter
46
VEGAMET
391
•
4
…
20
m
A / HART
signal conditioning instrument
8
A
pplication examples
36032
-
EN
-
091116