Fisher IM Supplement: Best Practices for use of Emerson 775 THUM WirelessHART Adapters with FIELDVUE Digital Valve Controllers Manuals & Guides

Instruction Manual

D104235X012

FIELDVUE Digital Valve Controllers

January 2021

Best Practices for use of Emerson 775 THUM

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WirelessHART® Adapters with FIELDVUE™ Digital
Valve Controllers

The Emerson Wireless 775 THUM Adapter is used to enable field devices communicating via the version 5, 6, or 7
wired HART
via a HART modem to the wired field device as well as via the WirelessHART radio to the WirelessHART network.

The THUM adapter is an external attachment to a field device and is not an integral component of it. Because of this
unique capability among WirelessHART devices and because of HART communication requirements of ValveLink
diagnostics with FIELDVUE digital valve controllers, there are “Best Practices” options related to integrating a THUM
adapter with FIELDVUE instruments that may differ from, or are in addition to, the traditional best practices for other
WirelessHART devices and networks.

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protocol to participate as members of a WirelessHART network. The THUM adapter communicates both

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Reference Documents

D DVC6200 HW2 FW7 Instruction Manual D103605X012

D DVC2000 Instruction Manual D103176X012

D DVC6200 SIS Instruction Manual D103557X012

D DVC6000 HW2 Instruction Manual D103785X012

D DVC6000 Instruction Manual (Supported) D102794X012

D DVC5000 Instruction Manual (Retired) D200442X012

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D Using OPC

D Emerson Wireless THUM Adapter Instruction Manual 00809-0100-4075

D Flyer: Emerson Wireless 775 THUM Adapter Unlock the Value in Your Existing Field Devices 00807-0200-4075

D White Paper: Smart Wireless THUM Adapter Effect on the 4-20 mA Loop

for Accessing Fisher FIELDVUE Digital Valve Controller Data D104429X012

www.Fisher.com

FIELDVUE Digital Valve Controllers

January 2021

Instruction Manual Supplement

D104235X012

Required Loop Power for THUM Adapters with FIELDVUE Instruments

In a patented design, rather than relying on battery power, a THUM adapter scavenges the electrical power it needs for
operation from the loop to which it is attached.

The configuration choice for the THUM adapter’s Voltage Drop parameter when used with FIELDVUE digital Valve
controllers should be set to “Variable Voltage Drop”.

Note

The THUM has no effect on loop current. Loop current flows through the THUM’s series loop connection (Red-Yellow Wire) thus
generating a 2 V drop. No loop current is returned through the parallel (Black-White connection). The Black/White pair are
capacitively coupled to the loop for wired HART communication purposes. Best practice is to recalibrate the Analog Input reading
of the FIELDVUE instrument while the THUM adapter is in circuit so that the FIELDVUE Instrument reads the control current at the
same level as the host commands.

The loop must be capable of supplying the power for both the THUM Adapter and the FIELDVUE Instrument sub-device
with which it is communicating.

FIELDVUE Instrument Type

Minimum required loop voltage to ensure

HART Communications (per Digital Valve

Controller Instruction Manuals)

Minimum required voltage for

powering both the FIELDVUE

Instrument and THUM Adapter

DVC6200 device type 1309
DVC6200 SIS device type 130A

10.0 VDC 12.0 VDC
DVC6000 HW2 device type 130B
DVC2000 device type 1305 9.0 VDC 11.0 VDC
DVC6000 device type 1303 11.0 VDC 13.0 VDC
DVC5000 device type 1302 12.0 VDC 14.0 VDC

Note

The minimum control current guaranteed without microprocessor restart for all FIELDVUE instruments is 3.5 mA. FIELDVUE
instruments should not be powered below this minimum control current level. The trigger point for the Low Travel Cutoff zero
pressure saturation (0.5% / 4.08 mA) is higher than the minimum control current value so there is no reason to power the
FIELDVUE instrument any lower than 3.5 mA. Doing so may risk processor restart and the loss of FIELDVUE and THUM
communications.

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