KROHNE H250H Handbook page 35

H250
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.
1 Terminal connection
2 Converter supply isolator with electrical isolation
3 Power supply (see supply isolator information)
4 Measuring signal 4...20 mA
5 External load, HART
Power supply
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).
The required supply voltage can be calculated using the formula below:
.
U = R 22 mA + 16 V
ext. L
where
U = the minimum supply voltage and
ext.
R = the total measuring loop resistance is.
L
INFORMATION!
The power supply has to be able to supply a minimum of 22 mA.
04/2009 - 4000269302 MA H250-R02
®
communication
www.krohne.com
ELECTRICAL CONNECTIONS
4
35