KROHNE H250 M8-M9-M10 EN - Manual (Page 35)

ELECTRICAL CONNECTIONS
4
35
H250
www.krohne.com 04/2011 - 4000269302 MA H250-R02 en
Power supply M10 with electrical isolation
The circuitry to other devices must be designed with special care. In some circumstances,
internal connections in these devices (e.g. GND with PE, ground loops) may lead to
impermissible voltage potentials, which can compromise the function of the device itself or a
connected device. In such cases a protected extra-low voltage (PELV) is recommended.
Power supply
The required supply voltage can be calculated using the formula below:
U
ext.
= R
L
. 22 mA + 16 V
where
U
ext.
= the minimum supply voltage and
R
L
= the total measuring loop resistance is.
1 Terminal connection
2 Converter supply isolator with electrical isolation
3 Power supply (see supply isolator information)
4 Measurement signal 4...20mA
5 External load, HART
® communication
INFORMATION!
The supply voltage has to be between 16 VDC and 32 VDC. This is based on the total resistance of
the measuring loop. To determine this, add up the resistances of each component in the
measuring loop (not including the device).
INFORMATION!
The power supply has to be able to supply a minimum of 22 mA.
MA_H250_R02_en_269302_PRT.book Page 35 Tuesday, April 12, 2011 10:17 AM