KROHNE BM 702 EN - Manual (Page 8)

8 Installation and operating instructions BM 702 (06/04)
When using the PTFE Wave-Stick in hazardous areas of Zone 0, any electrostatic charging of
the stick, e.g. by flow of product, must be avoided!
3 Electrical connection
To open the signal converter, please use a screwdriver and release the four visible screws
on top of the blue housing.
Terminal assignment
BM 702:
The polarity of the 4-20 mA connection
is arbitrary.
FE
1
2
4-20mA
current-
loop
cable gland
Equipotential bonding
When used in hazardous areas, the BM 702 Ex can be incorporated in the PA
equipotential bonding system, e.g. by using the separate U-clamp terminal at the “neck“
of the BM 702 Ex.
Rated temperature of connecting cables: see Section 6.
Supply voltage at the terminals (1,2)
The 4-20 mA supply must be able to provide the following voltage U at the terminals of the
BM 702 – dependent on the current I. Please consider also the line resistance and possible
loads on the secondary side of the supply unit.
4mA 12mA 8mA 16mA 20mA
3.6mA 22mA
I
U
13V
14V
15V
16V
17V
The allowed upper limit R for load+line resistance is depending on the specification of the
supply unit:
U at 20mA (supply unit)
14 V 15 V 16 V 17 V 18 V
Max. resistance R 50
Ω 100 Ω 150 Ω 200 Ω 250 Ω