KROHNE BM 26 A EN - Manual (Page 27)

Installation and Operating Instructions BM 26 A 27
3.4 Limit switch options for the BM 26 A (ATEX version)
Designation Housing
protection
Housing
material Power
cut-out Process
temperature Ambient
temperature Power supply
characteristics
MS20/EXI/LC/
PC/NN/BT EXI* PC 0.5A* ** ** U
i
I
i
C
i
L
i
****
100mA
0
0
MS15/EXI/LC/
PC/NO/BT EXI* PC NAMUR ** ** U
i
I
i
C
i
L
i
24V
***
0
0
MS15/EXI/
LC/AL/NN/HT EXI* ALU 1.5A*
** ** U
i
I
i
C
i
L
i
****
500mA
0
MS15/EXI/
LC/AL/NO/HT EXI* ALU NAMUR ** ** U
i
I
i
C
i
L
i
24V
***
0
0
MS15/EXD/LC/A
L/NN/HT EXD ALU 20VA
1.5A
250V AC ** ** U
max
I
max
P
max
380VAC
1,5 A
20 VA
MS15/EXD/LC/A
L/NO/HT EXD ALU NAMUR ** ** U
max
I
max
P
max
380VAC
1,5 A
20 VA
MS15/EXD/HC/A
L/NN/HT EXD ALU Max.:*****
Min.: 3 VA
1.5 A
250 V AC ** ** U
max
I
max
P
max
380VAC
1,5 A
20 VA
* To be connected to a certified intrinsically-safe power supply only.
** Dependant on ATEX temperature class. Refer to section 7.1 for further information.
*** The current value is not imposed, however the power supply must be intrinsically-safe.
**** The voltage value is not defined, however the power supply must be intrinsically-safe.
3.5 How to use a limit switch
3.5.1 Operating principle
The MS 15/STD, MS 15/EXI, MS 15/EXD, MS 20/STD and MS 20/EXI limit switches consist of a
reed contact that is actuated directly by the magnet system in the float. Due to their bi-stable
switching characteristic, the switching state is maintained until the float magnet system again
deactivates the limit switch in the opposite direction. Line-side connection of a suitable isolation
switching amplifier is recommended.
3.5.2 Installation
1 Attach the switch to the measuring tube at the desired level using the metal collar supplied.
2 Adjust the switch level to take into account the difference between indicated level and true level
(see section 1.6.4).
3 Adjust the switch level to take into account limit switch trigger point offset (see section 3.6.2).
Note: Due to its bi-stable characteristic, the switch can be operated in open-circuit or closed-
circuit mode (see section 3.5.5 Electrical connections), when appropriately connected.