KROHNE BM 102 Handbook - Manual (Page 20)

20 BM 102
2.2 Power Supply
2.2.1 Non-hazardous-duty
version
Power supply
Rated voltage 24 V DC
Max. voltage
(U
input
):
35 V DC
’Ex’ = 28 V DC
Min. voltage
(U
input
):
dependent on
load impedance,
see graph below
A supply voltage above 35 V DC can cause irreparable damage to the signal
converter. Also, power supply voltages above the specified max. values and below
the specified min. values can lead to faulty measurements or to a device reset.
Load impedance R
loop
Loop resistance, R
loop
R
HART
+ R
cable
+ R
ammeter
Min. R
loop
0 ohms
Max. R
loop
750 ohms
R
HART
resistance for HART® communication 250 ohms (recommended)
Line A = minimum voltage at the BM 102 terminals
Line B = voltage drop caused by a 250 ohm loop resistance