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Supplement to HART

Communicating Fisher

FIELDVUE

Digital Valve Controller Instruction

Manuals

FIELDVUE Digital Valve Controller Split Ranging

Processes requiring extended rangeability may use two or more control valves. The first valve operates over the first

portion of the range. When the first valve is nearly 100% open, the control action begins to open the second valve. This

is called split ranging. When split ranging is performed a single signal from the control system is supplied to the valve

actuators. This single signal is split among the positioning devices on each valve. The positioning devices are used to

achieve full valve travel over the reduced input range. Most applications need a predictable overlap region in the

middle of the signal range to avoid a zone of no control. Positioning devices provide accuracy to ensure the correct

overlap exists.

When split ranging FIELDVUE digital valve controllers, each device requires a minimum voltage available at the

instrument terminals of at least 12 volts (See the appropriate instruction manual for details). Many control systems

provide a compliance voltage that is less than the minimum requirement of 24 volts for two instruments wired in

series. This supplement describes two methods to address the potential discrepancy between the compliance voltage

and the requirements of FIELDVUE instruments.

Limitations of Split Ranging FIELDVUE Digital Valve Controllers

Split ranging FIELDVUE digital valve controllers provides the following limitations:

 Most control systems cannot provide the 24 volt compliance voltage. A device to boost the compliance voltage may

be required, such as the Action Instruments Action Pak



AP4380-2000.

 To communicate with multiple HART instruments on one pair of wires may require the polling addresses for the

instruments be nonzero. This means the instrument polling addresses must be reset and the HART devices (either

the 475/375 Field Communicator or ValveLink software with a HART modem) must be programmed to poll for

instruments at polling addresses other than zero.

 Use of the HART Tri‐Loop

 is limited to communication with only one instrument.

 The instrument polling addresses may be nonzero, thus limiting communication with a HART multiplexer.

Guidelines for Split Ranging FIELDVUE Instruments

1. Check the voltage available at the instrument terminals using the method in the instrument instruction manual.

2. Verify that the control system compliance voltage is at least 24 volts DC at 20 mA output. If the compliance voltage

is less than 24 volts DC, add a device to boost the compliance voltage (such as the Action Instruments Model

AP4380‐2000). (Note: the AP4380‐2000 does not have any hazardous area approvals. Appropriate non‐hazardous

installations should be selected.)

Instruction Manual Supplement

D103262X012

FIELDVUE Digital Valve Controllers

February 2011

Summary of content (6 pages)

PAGE 1
Instruction Manual Supplement FIELDVUE Digital Valve Controllers D103262X012 February 2011 Supplement to HARTr Communicating Fisherr FIELDVUEt Digital Valve Controller Instruction Manuals FIELDVUE Digital Valve Controller Split Ranging Processes requiring extended rangeability may use two or more control valves. The first valve operates over the first portion of the range. When the first valve is nearly 100% open, the control action begins to open the second valve. This is called split ranging.
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FIELDVUE Digital Valve Controllers Instruction Manual Supplement February 2011 D103262X012 3. Verify that cable length will not limit HART communication. See the instruction manual for details. 4. For intrinsically safe installations, install approved intrinsic safety barriers between the non‐hazardous and hazardous areas. Methods of Split Ranging Two methods are available for split ranging FIELDVUE instruments: the traditional method and an alternate method.
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Instruction Manual Supplement FIELDVUE Digital Valve Controllers D103262X012 February 2011 compliance voltage of the AP4380-2000 prior to shipment. This should be done using the technique described in the instrument instruction manual. Generally, a compliance voltage of 25 volts DC at 20 mA output with a guaranteed line voltage of 120 volts AC is adequate for normal lengths of field wiring.
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Instruction Manual Supplement FIELDVUE Digital Valve Controllers February 2011 D103262X012 Installation—Alternate Method When connecting two instruments in series for this split range application, the compliance voltage requirement from the DCS controller is much lower. This is because the Action Instruments AP4380‐2000 is in series with the first FIELDVUE instrument and requires minimum voltage (0.3 volts). The isolator powers only the second FIELDVUE instrument and therefore provides adequate voltage.
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Instruction Manual Supplement FIELDVUE Digital Valve Controllers D103262X012 February 2011 Configuration Current flowing through the input terminal of the isolator is regenerated at the output terminals of the isolator (at a higher voltage) and flows through the second FIELDVUE instrument only. Input ranging of the FIELDVUE instruments is easily changed without recalibrating. This is done by configuring the Input Range Low and the Input Range High to the desired values.
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FIELDVUE Digital Valve Controllers Instruction Manual Supplement February 2011 D103262X012 Related Fisher Documents FIELDVUE DVC5000 Series Digital Valve Controllers Instruction Manual Note The DVC5000 digital valve controller is obsolete. Contact your Emerson Process Management sales office if a copy of this instruction manual is needed.