SVI-II Instruc Man.book - Fagerberg
SVI-II Instruc Man.book - Fagerberg
SVI-II Instruc Man.book - Fagerberg
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Masoneilan Dresser<br />
<strong>SVI</strong> <strong>II</strong> AP <strong>Instruc</strong>tion <strong>Man</strong>ual<br />
Cabling and Interconnection Requirements<br />
Interconnections are made using shielded twisted pair cables. The shield is<br />
connected to ground at one point only. The signal loop is grounded at only one<br />
point in accordance with plant electrical standards. It is customary to ground<br />
the signal at the controller or intrinsic safety barrier. The <strong>SVI</strong> <strong>II</strong> AP is supplied<br />
with two 1/2 inch NPT conduit entries. M20 adapters are available. Internal<br />
and external ground terminals are provided for case grounding requirements.<br />
Install the <strong>SVI</strong> <strong>II</strong> AP in accordance with local and national code in both general<br />
and hazardous area locations. Substitution of components can impair<br />
suitability for use in hazardous locations.<br />
Note:<br />
The internal electronic components are isolated for ground.<br />
Grounding the case is unnecessary for functional purposes.<br />
Grounding the case may be necessary to conform to local codes.<br />
Capacitance vs. Length of Cable for HART<br />
The HART Communications Foundations specifies cable capacitance<br />
requirements to preserve signal strength. Refer to the standards for detailed<br />
calculation methods.<br />
Do not connect a HART modem and a PC to a control circuit unless the<br />
controller is HART compatible or has a HART filter. Loss of control or a<br />
process upset can occur if the controller output circuit is not compatible with<br />
HART signals.<br />
HART Filter Required for Certain Control System Output Circuits<br />
The <strong>SVI</strong> <strong>II</strong> AP is intended for use with all control systems. However, output<br />
circuits of several major DCS systems are incompatible with the tones used<br />
for HART signals. You must verify that the DCS or controller works reliably<br />
with the HART protocol. When the DCS is incompatible an external HART filter<br />
must be installed between the field wiring and the output card. MTL<br />
manufactures the HART filter HCU16AO. It is a 16 channel DIN rail mounted<br />
device composed of passive circuitry that introduces negligible voltage drop.<br />
For additional information, contact MTL.<br />
Note:<br />
A control circuit must be HART compatible or have a HART filter<br />
installed. Contact the manufacturer of the controller or DCS. See<br />
“HART Filter Requirements” on page 85. of this manual for more<br />
information<br />
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