Baumer LSP - Manual (Page 3)

Page 3 Design and specifi cations subject to change without notice
Installation Manual www.baumerprocess.com
1: Brown
2: White
3: Blue
4: Black
Electrical Installation
3
4 1
2
18...36 Vdc (+) (+) 4...20 mA
1 2 3 4
18...36 Vdc
+ -
4...20 mA
+ -
(-)18...36 Vdc 4...20 mA (-)
Connector LED Buttons M12 plug
Setpoint
100%; 20 mA
Setpoint
0%; 4 mA
Push buttons >3 sec.
to set 0% and 100%
Push both > 3 sec.
to reset.
Operator Control
The green LED indicates that a supply voltage > 18 V with the correct
polarity is present.
The two red LEDs show different fl ashing rates according to the control
of the 4...20 mA output.
The sensor can be installed in the top or the buttom of the tank.
The sensor is calibrated for installation from the top. Then 4 mA output
corresponds to the tip of the rod, and 20 mA to the thread end.
When installed from the buttom of the tank an output excessive of 4
mA is obtained.
The sensor can be calibrated by pressing one of the two setpoint keys
for more than 3 seconds. The relevant LED will show a steady light.
With these two buttons any empty/full level can be confi gured on the
entire length of the rod.
The factory setting will be valid again by pressing both keys for more
than 3 seconds.
The “dry” signal level is adjusted together with the low level setting.
The “dry” indication is 2.4 mA output current.
Caution
If different medias are used the low level adjustment should be made
with the media having the lowest conductivity.
Caution
The minus pole of the power supply is connected to the housing via a
protective diode.
However, the 4...20 mA output is galvanically isolated from the power
supply.
Measuring Principle
Theory
The liquid is stored in a ground connected tank.
The immersed level probe is a low resistance rod where the ends
are powered by an AC generator operating in the lower kiloherz
frequency range.
Between the rod and the tank wall is an endless amount of high level
resistances. Since they connect to the same potential (the tank wall)
they can be shown as two equivalent resistances, R1 and R2 con-
nected to an imaginary center point.
A high resistance input amplifi er is connected between the generator
and the tank wall.
Since the generator is supplying a high range current it will create a
signifi cant voltage drop across the low resistance rod.
The resistances R1 and R2 form a voltage divider in range of the
immersed part of the rod. Output from this divider will indicate half
the level of the liquid. The amplifi er then calculate the actual level of
liquid from 0 to 100%.
The formula is:
Uout= 1/2 x media level (%) x Ugen
Media level (%) = Uout/Ugen x 2
The level measurement is insensitive to adhesion.
Caution
It is very essential that the media conductivity is homogenious.
Otherwise R1 will not be equal to R2 and the output voltage will be
infl uenced.
R2
R1
Uout
to amplifi er
Ugen
100%
0%
X%