Barksdale UNS-VA/SB4 Operating Instructions Manual - Page 3
Browse online or download pdf Operating Instructions Manual for Switch Barksdale UNS-VA/SB4. Barksdale UNS-VA/SB4 6 pages. Level switch
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Principle of Operation
Figure 1: Sectional drawing - Level switch
All Barksdale level switches work according to the principle shown in picture 1.
A float equipped with magnets moves variably with the changing liquid level. The magnetic field of
the float actuates a reed switch positioned inside the guide tube at a predefined place and closes or
interrupts the current circuit.
If several level switching points are arranged in the stem various alarm functions can be triggered.
By adding suitable relays the signals can be used in control system or for automatic pump control.
Advantages of these switching units: separation from the medium, no mechanical stress
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Installation/Commissioning
IMPORTANT
All level switches are tested for proper functioning before they leave the factory.
DANGER
Prior to any work on electrical components disconnect them from power supply.
The electrical connection may only be made by trained expert staff!
4
1
Cable
2
Stem
3
Float
4
Magnet
5
Reed switch
The Barksdale level switches are supplied completely assembled. The level switches are installed
through the tank top or bottom side. Sufficient distance must be kept to the tank wall and any
installations. The float must move freely.
The Barksdale level switches should be installed vertically, if possible. Proper functioning is,
however, guaranteed up to an inclination of 30°.
Contact Protection
The values for current, voltage and power stated on the type label apply to purely resistive loads.
Frequently, lamp loads or the like should be switched as well. In these cases protection of the reed
switches against voltage and current peaks must be considered.
Below some examples are shown concerning the wiring of reed switches for various loads to avoid
premature failure.
RS
R1
C cable
R3
Load
R2
Figure 2: Protection in case of capacitive loads
R1: Protection against start-up current
rushes
R2, R3: Protection against discharge
currents
RS
U
=
Diode
Load
Figure 4: Protection at DC and inductive load
by recovery diode
RS
RS
R1
R2
Figure 3: Lamp load with parallel or series
resistor to switch
RS
U
C
R
Load
Figure 5: Protection at AC and inductive load
by RC-link.
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