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S4a SUBJECT TO CHANGE WITHOUT NOTICE Pag. 2 di 4

OPERATING PRINCIPLEA conveyor scale measures the flow rate andquantity of material transported by a beltconveyor.The "S" conveyor scale uses the most updatedthecniques and is made by three key parts: the

belt load sensor, the speed transmitter and theelectronic unit.The belt load receptor supports one or moreidler stations and delivers an electrical signalproportional to belt load.The speed transmitter is installed on a freerunning drum of the conveyor and delivers a pulsesignal proportional to the drum speed and, thus,to the belt speed.The electronic unit receives both signals andcalculates flow rate and total quantity passed overthe scale.Actually a modern conveyor scale have to perform

other standard functions absolutely necessarysuch as the automatic zero and span calibrationproceedures, the measurement of the speed andbelt load, the self diagnostic of the operation, etc.The "S" conveyor scale performs, over allstandard functions, the following unique features:Separate weight measurement of each loadcell: The instrument measures the output of eachload cell allowing, thus, an easy understanding ofsystem problems such as uncorrect loaddistribution among the load cells.Span self-calibration: The instrument performsthe weight and flow rate measurements directlyon the basis of load cells and conveyor dataentered and, thus, may not need field calibrationdepending on required accuracy and good qualityof installation.Span self calibration guaranties system accuracysimilar to those obtained by test weightcalibration.

Complete instrument handling by serial ports:All instrument setting, calibration and controloperations may be performed directly by thecontrol room supervisor through the RS485 serialport or locally, by a portable PC, through theRS232 port.Load cell and wiring failure control: Theinstrument continuously controls load celloperation and will alarm through the hardwareoutput or serial port any interruption or shortcircuit inside a load cell or relevant wiring.

THE BELT LOAD RECEPTORThe belt load receptor model RCN3 is a ready-to-mount assembly made by a stainless steel,plasma welded load cell with necessary horizontalconstraints and load cell overload control, whichcan directly support one idler station.

The design guaranties an accurate belt loadmeasurement independent from variations of thebelt load center of gravity.The conveyor scale may include one or two beltload receptor and one or more weighed idlerstations depending on flow rate, belt speed andaccuracy required.Normally for belt width over 800 mm and beltloading over 50 kg/m, is necessary to install twobelt load receptors on one idler station, while over2 m/sec is necessary to measure the belt loadover two idler stations.High accuracy scales (0,5%) always require two

belt load receptors, while superior accuracyscales (0,25%) require the use of the modelRCN4 belt load receptor, which is a complete selfsupporting platform scale with four load cells atthe corners and four weighed idler stations.

THE SPEED TRANSMITTERThe speed transmitter model TVN1 is made by ahigh sensitivity proximity switch, which sensesmetal pieces mounted on a free running drum ofthe conveyor (tail or counterweight drum), thusguaranting no error measurement produced byslippage.The transmitter generates one pulse per metalpiece in such a way thet the frequency of thesignal is proportional to belt speed; this methodguaraties zero error also in case of wide speedvariations (belt feeders).The operating frequency of the "S" conveyor scaleis from 1 to 50 Hz.Low speed conveyors require the installation ofmodel TVE1 speed transmitter (encoder type)which has a shaft connection and produces 50 ormore pulses per revolution depending on the

requirement of the application.

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THE ELECTRONIC UNIT

HARDWAREThe hardware of the instrument is made by:The base board equipped with a load cell inputmultiplexer, a "sigma delta" 16 bits A/D converterfor ratiometric measurement, an eight bit "RISC"microprocessor, EEPROM memory for power fai-lure-proof data retention, optoisolated RS485serial ports, load cell power supply with shortcircuit protection and an auxiliary 24 V d.c.isolated power supply for external input contactsand one analog 0/4-20 mA output.Remote indicator, 16 characters, 2 rows, LCD di-splay plus eight key keyboard.The optoisolated input/output board with fourcontact inputs, 1 open collector failurealarm output, 10 open collector outputs and one

analog 0/4-20 mA output.

SOFTWAREThe software of the "S" conveyor scale is quitewide and, over all commonly used conveyor scalefunctions, has several other functions which allowan easy integration in any plant general controlsystems, the analysis of installation problems andan easy setting of operating parametes specific tothe actual plant conditions.Main functions provided are the followings:- Flow rate, belt speed and belt load

measurement- Resettable and non-resettable totalizer- Automatic zero tracking- Automatic zero and span calibration

proceedures- Electronic span self-calibration- Span calibration proceedures for test weight,

calibration chain and material test- Measurement of tare and weight of each load

cell- High/low flow rate alarm- Failure alarm output- Load cell current measurement

-Load cell and relevant wiring failure alarm

- Lack of speed transmitter pulse alarm- Contact input for totalizer reset- Contact input for alarm reset

THE MAN / INSTRUMENTCOMUNICATIONIt should be noted that any operation required(set-up, calibration and controls) may beperformed both locally or remotly by means of theoptional indicator and/or by the serial ports.

The instrument is equipped with a RS485 port fornetwork connection to other equipments.The instrument may be supplied with a program(Window environments) which includes, inaddition to all standard procedures (set-up,calibration and controls), several functions forproblem analisys and complete instrumentaccess.

SCALE ACCURACYThe accuracy of a conveyor scale is strongly

dependent on application conditions andcalibration method available; thus, on approvedapplications, the accuracy guarantied by Celmi(typical value ranging from 0,25% to 1%) on thetotalized value refers to the following testconditions:- at least three complete belt revolutions- at least 500 totalizer counts- at least 10 minutes of conveyor run- flow rate between 25% and 100% of full scale

MODEL NUMBER

The electronic unit and the remote indicator mayhave different hardware options as indicated inthe model number composition.Specify, also, the required functions to allowcorrect writing or interpretation errors.

ELECTRONIC UNIT S4a X X X XmA output No 1

Yes 2

Input load cell N 2 load cell 2N 4 load cell 4

Housing No 0Yes painted steel 1Yes stainless steel 2Yes resine box 3

Software Conveyor scale 3

REMOTE INDICATOR S3 X X XI/O board Yes - with mA out 1

Yes - without mA out 2

Software Conveyor scale 3

Power supply 110/220 Vac 024 Vac 1

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INSTALLATIONThe load receptor have to be installed andaccuratly aligned as specified in the instructionmanual.The speed transmitter have to be installed on ahigh diameter driven drum (tail or counterweight

drum) to avoid slippage.The electronic unit have to be installed on avertical plane at an height suitable for easyoperation (1 - 1,8 meters) in environments withtemperature within spec. limits and withouthumidity condensation, aggressive or explosivevapours.The supporting structure must not have highvibrations; eventually vibration smoothers shouldbe provided.The electronic unit is normally installed near theload receptor and can be directly connected toload cell cables, thus, avoiding the need for an

additional junction box.Long distance installation (such as intrinsecallysafe applications) may be easily accomplished bysuitable cable sizing and installation design.

WIRINGWiring have to be done on the basis of terminalboard connection diagram and according to localstandard and regulations.Always use needle type wire terminator and installan external switch with fuse on power supply

connection (eventually common to otherinstruments).WARNING: Load cell, analog output and serialsignal cables must run separate from powercables.

ELECTRONIC UNIT

BELT LOAD RECEPTOR

SPEED TRANSMITTER

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