TRUNKGUARD Passes Fieldbus Short-Circuit Tests by Evaluation International, an Independent Testing Agency

Independent tests prove that the TRUNKGUARD device coupler works seamlessly with a DeltaV control system during repeated short-circuit testing and extreme temperatures.

NORTH HILLS, CA-MooreHawke, a division of Moore Industries-International, recently submitted its TRUNKGUARD fieldbus device coupler to Evaluation International for testing to confirm its short-circuit capabilities and to demonstrate its compatibility with Emerson Process Management's DeltaV FOUNDATION fieldbus communications systems under the worst possible conditions.

According to Evaluation International, TRUNKGUARD continued to operate and maintain communications with DeltaV after multiple short circuits on spurs, temperatures from -40 to 70°C, and operation at upper and lower voltage limits. "DeltaV showed no diagnostic error messages relating to repeated and multiple operation of TRUNKGUARD's spur short-circuit protection," reported Ian Ramsay-Connell, consultant at Evaluation International.

Scott Saunders, VP Sales at Moore Industries, says that the tests were conducted to prove that TRUNKGUARD performs as advertised. "We tested TRUNKSAFE ourselves, and it has been tested by customers, but we wanted an independent agency to confirm that the unique short-circuit protection in TRUNKGUARD passes interoperability tests with one of the most popular fieldbus hosts," says Saunders.

TRUNKGUARD's short-circuit protection method differs from conventional fieldbus device couplers. Competitive device couplers use a "current limiting" technique that holds a fault on the segment permanently; the additional current draw from the faulted circuit can overload the segment power supply or cause other devices on the segment to fail because of a lack of power. TRUNKGUARD's short circuit protection method prevents segment failure caused by single device faults. Its unique "fold-back" technique automatically removes the faulted device from the segment, and does not permit any current flow to the device until the fault is corrected.

Tests by Evaluation International confirm what MooreHawke has seen demonstrated during customer testing: When a spur is short-circuited, segment voltage actually increases, because TRUNKGUARD removes the shorted device from the segment. This means that multiple short circuits on a segment cannot deprive other instruments of power and cause a complete segment failure, as with conventional device couplers.

Test Details (from the report)

The system under test used a DeltaV Series 2 H1 card connected to a total of 16 fieldbus devices through two MooreHawke TG208-DIN. For the purposes of the test, the segment was powered by an Emerson-approved power supply unit. 1000ft of Kerpenwek Fieldbus Type A cable was used within the test circuit.

Correct system operation was verified by measuring communications signals at various points, and monitoring DeltaV diagnostics/FBT-3 readings under a variety of segment loading, short circuit (spur and trunk) faults and segment termination conditions.

Additional extreme temperature (-40°C and +70°C) performance tests were conducted using an environmental chamber to verify correct operation of the TG short-circuit protection circuit and the auto-termination circuit.

Primary Conclusions (from the report)

o Hawke TRUNKGUARD Electronic Device Coupler reliably passed FF communication signals between DeltaV Series 2 H1 Card and FF field devices.

o Active field devices were unaffected by repeated and multiple operation & resetting of TRUNKGUARD spur short-circuit protection.
o DeltaV showed no diagnostic error messages relating to repeated and multiple operation or resetting of TRUNKGUARD spur short-circuit protection.

o Tests were repeated and witnessed at extreme temperatures of -40 degrees C and +70 degrees C with no performance degradation.
Tests at upper and lower voltage limits were performed offline for practicality purposes.

All tests were carried out in accordance with the prescribed script.
No anomalies were witnessed which arose from the Equipment Under Test. All possible evidence was recorded to substantiate the tests.

About Evaluation International

Evaluation International, based in the UK, is part of the International Instrument Users' Association. Evaluation International performs testing and evaluation services on instrumentation and devices. For more information, go to:

For more information, contact

Moore Industries-International, Inc.

16650 Schoenborn St.

North Hills, CA 91343


Telephone: (818) 894-7111

FAX: (818) 891-2816


Web Site:


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