User's Manual

CN2
CN1
10 20 30 40 50 60
Vmax
0
14
36
0
500
1000
1500
2000
2500
Loop supply (Vdc)
x
xx
xxx
Loop resistance ( )W
x
xx
xxx
No external resistance, No HART
External resistance for HART
communication and 4-20 mA
External resistance for 4-20 mA
®
®
PassiveActive
CN1 CN2
-
+
HART
4-20 mA
Electrical installation
Installation guide 970 SmartRadar ATi Page 11
Figure 4 Changing passive/active loop supply and selecting external loop resistor
Selecting external or internal loop supply is done by placing the connector with the brown wires for:
• external supply in: CN1 of ICU_HPO board (passive loop)
• internal supply in: CN2 of ICU_HPO board (active loop)
With active loop, the supply voltage in the loop is: 20 Vdc (±5%).
With passive loop, the minimum supply voltage is 8 Vdc; the maximum supply voltage is 64 Vdc.
Supply voltages over 30 Vdc, require external series resistor (figure 4).
HART communication requires a minimum series resistor of 250 Ω. Refer to figure 4, loop
®
resistance graph. When HART loop is external powered, minimum supply voltage is 14 Vdc and
®
maximum supply voltage is 36 Vdc with 250 Ω resistor. With higher external supply voltage, series
resistor must be increased. The maximum resistance for HART communication is 1100 Ω, which
®
corresponds to a maximum of 57 Vdc loop supply voltage.
The power rating of external resistor depends on resistance value; we recommend 1 W / kΩ.
Hard alarm output contact
Relay output (option): Potential free relay contact; contact rating: U = 50 Vac or 75 Vdc;
max
I = 3 A. Mind the isolation voltage of the cores in the cable; refer to the
max
International Standard IEC 61010-1.