Volume 4, Issue 1

Can You Afford

NOTNOTto Use Coriolis?

Accuracy, Multiple Variables,

and Digital Communications

Add Value and Reduce Costs

Chri

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lot of users already know first-hand about Coriolis flow-

meters and what they cando. Accurate volume flow,

mass flow, total flow, pressure, temper-ature, percent solids, concentration,and density measurements in high-turndown applications can be had in asingle, compact instrument with nostraight-run requirements and mini-mum process penetrations. Users areincreasingly aware that the meters areno longer fussy about installation and

set-up, offer high stability, can mini-mize pumping losses, and require verylittle maintenance.

However, despite a number of newmodels becoming available at lowercosts, Coriolis flowmeters are still largelyperceived as too expensive for generalplant use, especially for the averageOEM application.

But the same multivariable digital sig-nal technology that allowed analog-to-digital conversion, digital signal process-ing (DSP), and essential calculations to bemoved from a separate transmitter intothe sensor body can be used to eliminatethe transmitter altogether (Figure 1).

Machinery OEMs and end users can avoidthe transmitter’s cost, space, and wiringrequirements by connecting directly tothe sensor via a digital network.

Compared to conventional analogCoriolis sensors, the increased informa-tion and computing power available withmultivariable digital electronics improvesaccuracy and/or turndown (Figure 2),and the efficiencies of multivariable dig-ital sensors allow these installations to bemade intrinsically safe.

Direct connection further reduces

Coriolis flowmeter costs, making themdirectly comparable to less-capable flowmeasurement technologies (Figure 3). Ifan application assigns any value tomultiple variables, stability, low main-tenance, and high accuracy, then adirectly connected Coriolis meter maywell be the least expensive option.

KNOW WHAT YOU’RE DOING?Eliminating transmitters is only anoption if you’re comfortable workingwith digital protocols. “Micro Motionuses Modbus,” says Denis Henrot, vicepresident of technology at the Boulder,Colo.-based Coriolis flowmeter company,

which calls its new transmitter-lessoption MVD™ Direct Connect™. “MVDDirect Connect is a fresh look at inte-grating sensors directly into PLCs andDCSs. We are reducing all the non-value-added costs: bulky transmitter,extensive wiring, etc.”

Several years ago, when the companyintroduced its MVD technology, it offeredan alternative to the traditional analogsensor, separate transmitter, and specialnine-wire connecting cable. “MVDallows multiple variables on a single pairof wires vs. one-per-pair for traditionalsensors,” says Richard Maginnis, manag-er of MVD electronics at Micro Motion.“And digital integration, regardless ofcommunication protocol, eliminates D/Aand A/D conversions associated withanalog I/O.” The nine wires were replacedwith four: two for power, and two for thedigital signal.

With MVD Direct Connect, you cantie sensors into a PLC or DCS using thesystem’s Modbus utility, or set up con-nections with Micro Motion’s ProLink®II software. “We normally provide themeters preconfigured, but configura-tion can be done using ProLink II, asimple Modbus configuration tool,”says Maginnis. “It’s a graphical inter-face for configuration, alarms, anddiagnostics.

“Customers who are comfortablewith digital protocols don’t need thecost or limitations of an analog signal,”he says. “So they can get a more cost-effective and flexible solution.”

THE POWER OF MULTIVARIABLEDIGITAL TECHNOLOGYCoriolis meters determine mass flow bymeasuring the phase difference betweenthe AC voltages from pick-off coilsmounted on the meter’s mechanicalassembly. In conventional meters, this

2 FLOW FORUM Volume 4, Issue 1

Transmitters Become OptionalTransmitters Become OptionalDirect Digital Connection Reduces Costs by Tailoring Coriolis Flowmeters to Machinery and Networked Plant Applications

AA

FIGURE 1: SIMPLIFICATION CUTS COSTS

Using Micro Motion’s MVD Direct Connect technology (right) eliminates transmitters, interface

cards, wiring, and cabinet space. Savings can amount to $2,500-3,000 per flowmeter (see page 4).

FLOW FORUM Volume 4, Issue 1 3

phase difference is measured using aprecision counter that clocks the timedifference between the two pick-off sig-nals after they have been conditionedby the transmitter’s analog front end. Inthe Micro Motion MVD transmitter, the

pick-off signals are converted immedi-ately into digital representations,which are not subject to the drift andinstabilities inherent in analog sys-tems. These signals are then processedusing patented DSP methods.

The entire input voltage waveform isdigitized, as opposed to just the zero-crossing points where significant errorscan occur as a result of mechanical andhydraulic (i.e. water hammer) distur-bances in real-world applications. TheDSP front end filters out this noise andflow signal corruption, allowing a moreaccurate and repeatable measurement.

Multivariable digital flowmeters alsooffer self-diagnostics: they can monitorthemselves and their sensors to detectconditions that signal a problem beforeit becomes serious, or identify the sourceof a problem from the control room ormaintenance shop before sending out atechnician. This can be especially valu-able on equipment in remote or haz-ardous areas.

Self-diagnostics can reduce down-time and unneeded service by identify-ing which devices need attention duringshutdowns. The ability to quickly detectand pinpoint problems can keep

flowmeters more accurate more of thetime, improving process consistencyand availability.

With appropriate software, somemultivariable digital flowmeters candiagnose process problems, too.

“Traditional analog systems can onlynotify fail high/fail low,” says Maginnis.“Micro Motion MVD gives access to rootcauses and diagnostics that, along withcontrol system problems, can identifyprocess situations such as entrained air,clogging, or coating.”

The digital communications offer

data at very high speeds, suitable, forexample, for fast filling applications.“Speed of response and access toinformation is increased to about 50msec. from the 250-300 msec. typicalof analog instruments.”

Loop performance should also improvewith multivariable digital since a less fil-tered, faster responding, more repeatable

signal generally allows for process set-points closer to the desired target.

GO INTO HAZARDOUS AREASCompact, efficient digital electronicsallow the flow sensor to be intrinsicallysafe for installation in hazardous areas.But the core processor in the sensor isonly intrinsically safe when it is con-nected to a device that limits the amountof energy into the hazardous area. “Theintrinsic safety barrier is not a standard4-20 mA barrier,” says Maginnis. “TheMicro Motion MVD Direct Connect bar-rier provides intrinsically safe DC powerto the core processor and intrinsicallysafe RS-485 Modbus communications.”

The connection from the core proces-sor to a host system uses a standard four-wire signal cable that customers use forinstruments such as pressure and temper-ature transmitters. However, intrinsicallysafe installations require a ground con-nection between the host and the coreprocessor. This can be achieved by usingconduit piping, armored cable, or a sep-arate ground wire that is attached to thecore processor and the host.

Many users are unfamiliar with

intrinsic safety and prefer explosion-proofing, but, “The core processor isintrinsically safe and not explosion-proof because this method provides themost cost-effective solution,” saysHenrot. “There are also many customersthat do not accept any other protectionmethod because intrinsic safety pro-vides the highest level of safety.” ◆

MVD Transmitter0.1% accuracy

Analog Transmitter0.21% accuracy at same flow rate

% of nominal flow10 200

0.6

0.4

0.2

0.0

-0.2

-0.4

-0.630 40 50 60 70 80 90 100

FIGURE 2: DIGITAL VS. ANALOG ACCURACY

Converting the signal and processing it within the flow sensor boosts Coriolis accuracy.

$6,000

$5,000

$4,000

$3,000

$2,000

$1,000

$01-in. meter

Traditional Coriolis

Multivariable DP

Coriolis with Direct Connect

PD meter

Turbine meter

FIGURE 3: COSTS ARE GETTING CLOSE

Eliminating the transmitter brings the purchase cost for Coriolis meters very close to differential

pressure (DP), positive displacement (PD), and turbine meters.

NL-00469

Better BlendersBetter Blenders

FOR MORE INFORMATION ON MICRO MOTION PRODUCTS, CALL MICRO MOTION AT 1-800-760-8119.

MM any original equipmentmanufacturers (OEMs)of processing equip-ment focus on being the

low bidder, and put their productstogether using the least expensiveinstrumentation and controls they canget away with. But a few have learnedthat outstanding engineering, accuracy,consistency, and durability have recog-nized value among end users, and haveearned reputations for building superi-or equipment that more than justifiesits premium price. KHS (www.khs-inc.com) is in that second group.

“We make fairly aggressive state-ments of performance for all of theequipment we build, and we build aCadillac,” says KHS product managerJeffrey Tietz. “The way our customersjustify the additional cost is consistencyand accuracy.”

The Waukesha, Wis.-based companyproduces a wide range of process andpackaging equipment and equips itsbatch blending equipment with Coriolismass flowmeters. “The heart of what wedo is based on mass flow,” says JodyLawson, KHS senior electrical engineer.“Volumetric flow is affected by temper-ature, mass is not. We use Coriolis formass flow accuracy.”

Along with mass flow, the Coriolismeters measure volume flow, tempera-ture, and density. Many customers addhigh-fructose corn syrup as an ingredi-ent. “From temperature and density wecan calculate percent solids of the cornsyrup, which lets us control finishedproduct brix,” says Lawson. “Theblending system can automaticallycompensate for variations in tank-loadsof corn syrup.”

“Our customers are concerned aboutaccuracy,” says Tietz. “Controllingexpensive ingredients like essences orstaying closer to the specification—not

running rich—on components like cornsyrup goes right to their bottom lines.”

KHS recently started using Boulder,Colo.-based Micro Motion’s MVD DirectConnect system to integrate Coriolisflowmeters with control systems viaModbus. Prior to using MVD DirectConnect, each flowmeter had a trans-mitter mounted in the control cabinet

(a single piece of equipment will usetwo to 13 flow sensors). The transmittersfed a pulsed input through an interfacecard to a PLC, where it was scaled andconverted to mass flow. Temperatureand density 4-20 mA signals were alsobrought in through cards. “The newtechnology lets us eliminate the trans-mitters, the cards, and the special nine-wire cable from the sensor to the trans-mitter,” says Lawson. “We now use asmaller rack and we’re able to decreasethe cabinet size.”

Lawson uses Micro Motion’s ProLinkII package to set up the meters. “All wehave to do is apply 24 VDC over two

wires, and connect two wires for theModbus signal. We use the ProLink IIconfiguration software, go online withthe meter, and assign an address,” hesays. “All the configuration data for themeter body is programmed in themeter; we just assign an address.”

Along with simplifying hardwareand configuration, Lawson says theMVD Direct Connect approach reducesengineering hassles. “It makes my job alot easier by streamlining things. Idon’t have to worry about scaling—itgives me real-time data in engineeringunits. I can look at the meter and seewhat it sees.”

The rapid updates and digital signalsalso add accuracy, especially in fastapplications. Tietz says, “In the meter’soptimum range, where we design themto run, MVD Direct Connect is 100%more accurate.”

But regardless of how accurate aninstrument is or how elegant the engi-neering, no company can afford to useequipment that doesn’t contribute itsshare to ROI. For KHS, Micro Motion’sMVD Direct Connect simply savesmoney, Lawson says. “Cost savings areterrific, about $2,500-3,000 per meterinstalled, by eliminating the transmitterand interface cards, reducing the cabi-net size, and simplifying the wiring.” ◆

Web-CornerSAVE SPACE AND MONEY

Visit www.micromotion.com/oem to learn more about how Micro Motion's MVD Direct Connect can:

◆ Reduce skid footprint◆ Simplify system integration◆ Lower wiring costs

Web-Corner

KHS Reduces Costs, Improves Accuracy, and Adds Value With Micro Motion MVD Direct Connect Technology

PRECISION TOOL

Waukesha, Wis.-based KHS can promise to

save customers costly ingredients because its

blenders are equipped with multivariable digi-

tal Coriolis flow sensors connected directly to

the control system via Modbus. The approach

saves KHS $2,500-3,000 per flowmeter.