En
gl
is
h (
G
B)
24
6.4.3 Analog 0/4-20 mA
In this operation mode, the pump doses
according to the external analog signal.
The dosing volume is proportional to the signal input
value in mA.
If the input value in operation mode 4-20 mA falls
below 2 mA, an alarm is displayed and the pump
stops. A cable break or signal transmitter error has
occurred. The "Cable break" symbol is displayed in
the "Signal and error display" area of the display.
Fig. 17
Analog scaling
Fig. 18
Analog operation mode
Set analog scaling
Analog scaling refers to the assignment of the
current input value to the dosing flow.
Changes of analog scaling affect also the analog
output signal. See section
Analog scaling passes through the two reference
points (I
1
/Q
1
) and (I
2
/Q
2
), which are set in the "
Setup
>
Analog scaling
" menu. The dosing flow is
controlled according to this setting.
Example 1 (DDA 7.5-16)
Analog scaling with positive gradient:
Fig. 19
Analog scaling with pos. gradient
In example 1, the reference points I
1
= 6 mA,
Q
1
= 1.5 l/h and I
2
= 16 mA, Q
2
= 7.5 l/h have been
set.
From 0 to 6 mA analog scaling is described by a line
that passes through Q = 0 l/h, between 6 mA and
16 mA it rises proportionally from 1.5 l/h to 7.5 l/h
and from 16 mA onwards it passes through
Q = 7.5 l/h.
Example 2 (DDA 7.5-16)
Analog scaling with negative gradient (Operation
mode 0-20 mA):
Fig. 20
Analog scaling with neg. gradient
In example 2, the reference points I
1
= 2 mA,
Q
1
= 7.5 l/h and I
2
= 16 mA, Q
2
= 1.3 l/h have been
set.
From 0 to 2 mA analog scaling is described by a line
that passes through Q = 0 l/h, between 2 mA and
16 mA it drops proportionally from 7.5 l/h to 1.3 l/h
and from 16 mA onwards it passes through
Q
2
= 1.3 l/h.
Operation
mode
Input value
[mA]
Dosing flow
[%]
4-20 mA
≤
4.1
0
≥
19.8
100
0-20 mA
≤
0.1
0
≥
19.8
100
T
M
0
4
1
1
20
20
10
T
M
0
4
11
2
7
111
0
0
Q [%]
0 - 20 mA
4 - 20 mA
[mA]
4
20
8
12
16
100
80
0
60
40
20
Operation
6.50
ml/h
0-20mA
17.14mA
T
M
0
4
1
1
60
20
10
T
M
0
4
1
1
01
20
10
Q [l/h]
16
1.5
6
7.5
5
0
0
20 I [mA]
(I
2
/Q
2
)
(I
1
/Q
1
)
0
0
20
16
1,3
2
7,5
I [mA]
Q [l/h]
(I
2
/Q
2
)
(I
1
/Q
1
)
