KROHNE H250 M8-M9-M10 EN - Manual (Page 28)

4
ELECTRICAL CONNECTIONS
28
H250
www.krohne.com 04/2011 - 4000269302 MA H250-R02 en
Power supply
The required supply voltage can be calculated using the formula below:
U
ext.
= R
L
. 22 mA + 12 V
where
U
ext.
= the minimum supply voltage and
R
L
= the total measuring loop resistance is.
HART ® communication
When HART ® communication is carried out with the ESK, the analogue measured data
transmission (4...20 mA) is not impaired in any way.
Exception for multidrop mode. In multidrop mode, a maximum of 15 devices with HART ® function
can be operated in parallel, whereby their current outputs are switched inactive
(I approx. 4 mA per device).
INFORMATION!
The supply voltage has to be between 12 VDC and 30 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 28 Tuesday, April 12, 2011 10:17 AM