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Table 4 through Table 6 on page 46 provide examples of several SVI3 installations and
calculating the compliance voltage necessary to supply 9 V at 20 mA..
Conclusion
: The control system must have a compliance voltage equal to or greater than
17.64 V; contact the DCS vendor to verify compliance
.
Conclusion
: The compliance voltage issue is not present because the Isolator provides all
the necessary voltage.
Conclusion
: The control system must have a compliance voltage equal to or greater than
16.3 V; contact the DCS vendor to verify compliance.
Table 4: Compliance Voltage for Single Channel Zener with 22 AWG Cable
Voltage across SVI3 Control Terminals with 20mA Signal
9.0 V
Drop in single channel Zener barrier with 342 Ohms end to end resistance
6.84 V
Drop in 22 AWG cable
,
3000’ long (30 Ohms per 1000’)
1.8 V
Drop in passive
HART
®
Filter
0.0 V
Voltage required at controller
17.64 V
Table 5: Compliance Voltage for Galvanic Isolator with 22 AWG Cable
Voltage at SVI3 at 20mA
9.0 V
Drop in 22 AWG cable
,
3000’ long (30 Ohms per 1000’)
1.8 V
Required voltage at Isolator
10.8 V
Voltage available from Isolator rated to drive 22 mA into 700
Ohm
13.2 V
Voltage required at controller
Not applicable
-
Isolator sup
-
plies the power
Table 6: Compliance Voltage for No Barrier with HART
®
Filter and Resistor and 18 AWG Cable
Voltage at SVI3 at 20mA
9.0 V
Drop in 220 Ohm resistor
4.4 V
Drop in 18 AWG cable, 6000’ long (12 Ohms per 1000’)
0.6 V
Drop in passive
HART
®
Filter
2.3 V
Voltage required at controller
16.3 V
