4
ELECTRICAL CONNECTIONS
38
SITRANS FX330
www.siemens.com/flow
05/2016 - A5E36751269-AA
4.3 Electrical connections
The signal converter is a 2-wire device with 4...20 mA as output signal. All other inputs and
outputs are passive and always require an additional power supply.
4.3.1 Power supply
All versions are intended for connection to limited-energy circuits of max. 36 VDC / 4 A.
The required supply voltage can be calculated using the formula below:
U
ext.
= R
L
* 22 mA + 12 V
with
U
ext.
= the minimum supply voltage
R
L
= the total measuring loop resistance
4.3.2 Current output
Connect current loop 4..20 mA to terminals C1+ and C2-.
When connection cables are long, a shielded or twisted cable may be necessary. The cable shield
may only be grounded at one place (e.g. on the power supply unit).
INFORMATION!
The supply voltage has to be between 12 VDC and 36 VDC (12...30 VDC for Ex). This is based on
the total resistance of the measuring loop. To calculate this, the resistance of each component in
the measuring loop (not including the device) must be added up.
INFORMATION!
The power supply has to be able to supply a minimum of 22 mA.
Figure 4-2: Electrical connection current output
1
Power supply for current output
2
Optional display unit (R
L
)
3
Load for HART
®
≥
250
Ω