KROHNE BW 25 EN - Manual (Page 20)

4
ELECTRICAL CONNECTIONS
20
BW25
www.krohne.com 09/2010 - 4000432302 MA BW25 R05 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.
Load for HART ® communication
The maximum load resistance is calculated as follows:
Configuration
The ESK can be configured via HART ® communication. DD (Device Description) for AMS 6.x and
PDM 5.2 as well as a DTM (Device Type Manager) are available for configuration (go to download
centre at www.krohne.com).
With the integrated HART ® communication, the current level can be transmitted. Two limit
values can be monitored.
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 level meter).
INFORMATION!
The power supply has to be able to supply a minimum of 22 mA.
INFORMATION!
For HART
® communication a load of at least 230 ohm is required.
DANGER!
Use a twisted two-core cable to prevent electrical interference from impeding the DC output
signal.
In some cases a shielded cable may be necessary. The cable shield may only be earthed
(grounded) at one place (on the power supply unit).
MA_BW25_R05_en_432302_PRT.book Page 20 Tuesday, September 28, 2010 8:17 AM