Hardy HI1734 Installation And Operations Manual

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HI 1734-WSPOINT I/O Weigh Scale ModuleInstallation & Operations Manual9440 Carroll Park DriveSan Diego, CA 92121Phone: (858) 278-2900FAX: (858) 278-6700Web-Site: http://www.hardysolutions.comHardy Process Solutions Document Number: 0596-0354-01 Rev. ACopyright 2017 Hardy Process Solutions All Rights Reserved. Printed in the U.S.A.

Hardy 1734-WS Installation & Operation ManualLocal Field ServiceHardy Process Solutions provides local field service for all scales and weighing equipment. Hardy’s factorytrained technicians can perform service on all Hardy equipment as well as most other manufacturers’ systems.Enabled by the Hardy Process Toolbox, our technicians spend less time onsite, saving you money and reducingyour downtime.Services Include: Installation & CommissioningPreventative Maintenance & CalibrationOnsite Emergency ServiceService Agreements with Defined Turnaround TimesProduct, Service, and PLC Integration TrainingPre-Installation Site AuditScale Installed-Base EvaluationPLC Integration SupportEngineering Design Support & Specification DevelopmentQuality Documentation CreationContact UsTo request any of the services mentioned, or to discuss your needs with a trained Hardy Service Agent, pleasecall 800-821-5831 Option 4 (6:30 AM to 5:30 PM PST). For emergency downtime service after hours, leave amessage in our emergency mailbox and your call will be returned promptly. Or email us athardysupport@hardysolutions.com.Page 2

Hardy 1734-WS Installation & Operation ManualContents CAUTION:UNPACK WITH CARE . 5ATTENTION: DÉBALLEZ SOIGNEUSEMENT . 5Chapter 1 - Overview . 6Product Description . 7Waversaver . 7C2 Calibration . 7Chapter 2 - Specifications . 9Specifications . 9Environmental Requirements. 9Default Parameters . 10Chapter 3 - Installation . 11Installation Overview . 11Detailed Installation Procedure . 11Load Sensor Connections . 12Chapter 4 – Setup and Operation. 19Power Check . 19Setting Up Communications between the PLC and HI 1734-WS . 19Configuration Parameters . 22Configuration with AOP . 23Commands . 23Output Table . 26Input Table . 26Chapter 5 - Calibration . 28Pre-Calibration Procedures . 28Electrical Check Procedures . 29Load Sensor/Point Input/Output Measurements . 29Load Check . 29Calibration Setup Procedures . 30Page 3

Hardy 1734-WS Installation & Operation ManualC2 Calibration . 33C2 Calibration Using Ladder Logic . 33C2 Calibration Using the Faceplate . 33Hard Calibration. 35Hard Calibration Using Ladder Logic . 35Chapter 6 – Troubleshooting . 36Return Codes . 36Chapter 7 - Hardy Installation and Commissioning . 38Emergency Service and Support . 38Appendix A . 39List of the Parameter IDs . 39Read/Write Parameters. 39Read Only Parameters . 39Page 4

Hardy 1734-WS Installation & Operation ManualCAUTION:UNPACK WITH CAREWHEN UNPACKING, DO NOT DISCARD THE PACKING CASE OR ANY PACKING MATERIAL UNTIL THE CONTENTSOF THE PACKING CASE ARE INSPECTED AND CAREFULLY COMPARED WITH THE SHIPPING DOCUMENTS.IF ANYTHING IS UNSATISFACTORY, PLEASE NOTIFY HARDY IMMEDIATELY BY CALLING, FAXING OR E-MAILING TO:Customer Support DepartmentHARDY PROCESS SOLUTIONS9440 Carroll Park Drive, Suite 150 San Diego, California 92121Phone:FAX:(800) 821-5831(858) 278-2900(858) 278-6700E-mail: hardysupport@hardysolutions.comWeb Address: www.hardysolutions.comA RETURN MATERIAL AUTHORIZATION (RMA) NUMBER IS REQUIRED BEFORE RETURNING ANY DAMAGEDPRODUCT. CALL THE CUSTOMER SUPPORT DEPARTMENT TO GET AN RMA NUMBER. HAVE READY YOURCOMPANY NAME, ADDRESS, TELEPHONE NUMBER, SERIAL NUMBER OF THE UNIT AND A BRIEFDESCRIPTION OF THE PROBLEM WHEN CALLING.IN CASE OF DAMAGE DUE TO SHIPPING, NOTIFY THE DELIVERING CARRIER IMMEDIATELY FOR AN INSPECTION.ATTENTION: DÉBALLEZ SOIGNEUSEMENTVEUILLEZ CONSERVER L’EMBALLAGE PENDANT L’INSPECTION DU PRODUIT ET COMPAREZ RIGOUREUSEMENTAVEC LES DOCUMENTS ENVOYÉS.VEUILLEZ ALERTER IMMÉDIATEMENT L’AGENCE DE LIVRAISON AU CAS OU DES DOMMAGES DUES A LALIVRAISON SERAIENT PRÉSENTS.Customer Support DepartmentHARDY PROCESS SOLUTIONS9440 Carroll Park Drive, Suite 150 San Diego, California 92121Phone:FAX:(800) 821-5831(858) 278-2900(858) 278-6700E-mail: hardysupport@hardysolutions.com Lien: www.hardysolutions.comUN NUMÉRO UNIQUE (RMA ou RETURN MATERIAL AUTHORIZATION) EST NÉCESSAIRE AFIN DE RENVOYER LEPRODUIT ENDOMMAGÉ. CONTACTEZ LE SERVICE-CLIENTELE AFIN D’EN OBTENIR UN. VEUILLEZ VOUSPRÉMUNIR DES INFORMATIONS SUIVANTES AVANT L’APPEL : NON DE L’ENTERPRISE, ADRESSE, NUMÉRO DETELEPHONE, NUMÉRO DE SÉRIE DU PRODUIT, AINSI QU’UNE COURTE DESCRIPTION DU PROBLEME.Page 5

Hardy 1734-WS Installation & Operation ManualChapter 1 - OverviewThis manual is designed for use by installers, operators, and service personnel. It provides specifications andprocedures for linking, configuring, operating, maintaining, and troubleshooting the Hardy Process SolutionsHI1734-WS POINT I/O Weigh Scale Module. The system is used for front end signal processing of load cells andload sensors (strain-gage type sensors) for all types ofindustrial manufacturing weighing applicationsthrough an Allen Bradley 1734 POINT I/O chassis.Modules feature Waversaver , C2 Calibration,INTEGRATED TECHNICIAN (IT) diagnostics, andladder logic configurability. 1Before using the product, be sure you understandall cautions, warnings, and safety proceduresstated or referenced in this manual. And, to getthe best service from this product, follow thepractices recommended in this manual.Hardy Process Solutions appreciates your business.We welcome all corrections or suggestions forimprovement of this manual. Should you not understand any information in this manual or experience anyproblems with the product, please contact our Customer Support Department at:Phone: (858) 278-2900FAX: (858) 278-6700e-mail: hardysupport@hardysolutions.comWeb: www.hardysolutions.com1Waversaver and C2 are registered trademarks and INTEGRATED TECHNICIAN is a trademark of Hardy ProcessSolutions.Page 6

Hardy 1734-WS Installation & Operation ManualProduct DescriptionHI1734-WS Weigh Scale Modules are self-contained, microprocessor-based I/O modules that produce weightdata when connected to strain gauge load sensors (load cells, load points, platform scales), and are pluggedinto an Allen-Bradley Point I/O System.The Allen-Bradley Point I/O manual contains useful information about POINT I/O products that is notprovided in this manual. This manual assumes that users have a basic understanding of process control andcan interpret ladder logic instructions as needed to generate the electronic signals that control theirapplication(s).The HI1734-WS Weigh Scale Modules can be used for a wide variety of process weighing applications such asbatching, blending, filling/dispensing, check weighing, force measurement, level by weight and weight ratemonitoring.The analog-to-digital converter in the weighing module controller updates 70 times per second and is capableof up to 8,388,608 counts of resolution. This is enough to provide accurate weight measurement and controland tolerate large “dead” loads or over sizing of load sensors.Waversaver During the measurement of small weight changes, the effects of mechanical vibration and noise from theoperating environment can introduce substantial interference. Waversaver factors out vibration, noise, andother interference-related signals from the load cell so the rate controller can better compute the actualweight data.Waversaver can be configured to ignore noise with frequencies as low as 0.25 Hz. One of five higheradditional cut off frequencies may be selected to provide a faster instrument response time. The defaultfactory configuration is 1.0 Hz vibration frequency immunity. The five cutoff frequencies are: 0.25Hz, 0.5Hz,1Hz, 3.5Hz and 7.5Hz.C2 CalibrationTraditional calibration uses certified test weights. C2 Electronic Calibration allows a scale to be calibratedwithout the need for test weights.A C2 weighing system consists of up to eight C2 load sensors, a junction box, interconnect cable, and aninstrument with C2 capabilities. Each Hardy C2-certified load sensor outputs digital information used for thecalibration. The modules read the sensor outputs and detect the number of active sensors. It then calibrates thescale based on the load sensor’s output plus a user-supplied reference point value (from 0 to any known weighton the scale).Page 7

Hardy 1734-WS Installation & Operation ManualITINTEGRATED TECHNICIAN (IT) is a system diagnostics utility which, in conjunction with an HI 6010IT or HI 6020ITjunction box, continuously monitors the excitation circuit (with up to 4 load sensors for the 6010 and up to 8 loadsensors for the 6020) for possible malfunctions. IT reads individual load sensor voltages and weights and isolatesindividual system components for quick and easy troubleshooting.If you do not have the HI 6020IT or HI 6010IT Junction Box connected to the module, the mV/V reading isdisplayed as the total for all the load sensors on the system.Return to Zero Test – OptionalThis test requires the HI 6020IT or HI 6010IT Series Junction Box to monitor individual load sensors. It comparesthe original voltage reading (saved at calibration) against the current voltage reading of an empty vessel. Thetest checks for damaged load sensors due to electrical zero shift or abnormal mechanical forces that causebinding on one or all of the load sensors in the system.NOTE: The HI 1734-WS IS compatible with the Hardy HI 6020IT, HI 6020JB HI 6010 IT or HI 6010JB. Youmust use the HI 6020IT or the HI 6010IT to run this particular test. The HI 1734-WS is notcompatible with the Hardy HI 215IT Junction Box. It is compatible with the HI 215JB without theIT functions.Weighing System Test – OptionalFor full utilization, this test requires the HI 6020IT or the HI 6010IT Series Junction Box. The Weighing Systemtest is used to diagnose drifting or unstable weight reading problems. The Weighing System Test does thefollowing:1. Disconnects the load sensors and engages an internal (in the junction box) reference signal to see if thecable between the instrument and the Junction Box is causing the problem.2. Reads the weight of each load sensor to see if the load sensor might be causing the problem.The ability to read the weight seen by each individual load sensor allows use of this test to make cornering,leveling and load sharing adjustments to the weighing system.Auto Zero TrackingAuto Zero Tracking automatically adjusts for zero weight. This capability allows the module to ignore materialbuild-up in the weighing system within a pre-set auto zero tolerance. For auto zero to work, the current grossweight must be within the auto zero tolerance. The current gross, plus any previously zeroed weight must bewithin the Zero Tolerance level value and the scale must not be in motion. This is not used on all applicationsand should be reviewed before use.NOTE: The amount of weight zeroed off is cumulative. The Auto Zero command will not run if the current grossweight plus any previously zeroed amount exceeds the zero tolerance value.Page 8

Hardy 1734-WS Installation & Operation ManualChapter 2 - SpecificationsChapter 2 lists the specifications for the HI1734-WS Weigh Scale Module. Specifications are listed for thestandard instrument and for optional equipment. The specifications listed are designed to assist in theinstallation, operation and troubleshooting of the instrument.SpecificationsChannels:1Conversion Rate:55 updates per second internally, 50 updates per second to PLC.Averages:1-255 User Selectable in single incrementsResolution Internal:1:8,388,608Input:Up to eight (8) 350 ohm Full Wheatstone Bridge, Strain Gauge LoadSensors/Cells (5 volt excitation) on one scale (using two junction boxeswith a TB-10 connector)Non-Linearity:0.001% of Full ScaleWaversaver :User Selectable Off 7.50 Hz 3.50 Hz 1.00 Hz (Default) 0.50 Hz 0.25 HzBackplane Electrical Ratings:24 VDC, 100 mA5 VDC, 100 mACable lengths:250 feet maximum of C2 authorized cable (Maximum of 8 load sensors)with IT Junction box.Load Cell Excitation:5 VDCIsolation from digital section1000 VDC minimumC2 Calibration Output:Isolation from digital section 1000 VDC minimumTemperature Drift:Less than 0.0004% of full scale per degree C for Cal- LO and Cal-HIreference pointsEnvironmental RequirementsOperating Temperature Range:-20 C to 55 C (-4 F to 131 F)Storage Temperature Range:-40 C to 85 C (-40 F to 185 F)Page 9

Hardy 1734-WS Installation & Operation ManualHumidity Range:0-90% (non-condensing)Approvals:UL, CUL Ordinary LocationDefault ParametersConfiguration TableGravity CorrectionMotion ToleranceZero ToleranceTare WeightReference WeightSpan WeightAutoZero ToleranceEnable 90-10-5BYTE4Load Cell SensitivityWaversaverNum Averages0-8BYTEBYTEINT30-5101-2550 – Off1 - On0 – oz1 – lb2 – ton3–g4 – kg5-t0 – 1.0 mV/V1 – 1.5 mV/V2 – 2.0 mV/V3 – 2.5 mV/V4 – 3.0 mV/V5 – 3.5 mV/V6 – 4.0 mV/V7 – 4.5 mV/V8 – 5.0 mV/V0 – Off1 – 7Hz2 – 3.5 Hz3 – 1Hz4 – 0.5Hz5 – 0.25HzNOTE: THE HI1734 is not compatible with HI 215IT Junction Boxes. Please ensure that the HI1734 isinstalled with the HI6020IT, HI 6020JB, HI 6010IT or HI 6010JB Junction Boxes. It is compatiblewith the HI 215JB without the IT functions.Page 10

Hardy 1734-WS Installation & Operation ManualChapter 3 - InstallationChapter 3 provides the recommended procedures for unpacking, cabling, interconnecting, configuring andinstalling the Weigh Scale Module. Users and service personnel should be familiar with this information beforeinstalling or operating the Weigh Scale module. If you experience any problems installing this equipment,contact Hardy Process Solutions Technical Support for assistance.Installation OverviewWARNING - ELECTROSTATIC DISCHARGE MAY DAMAGE SEMICONDUCTORCOMPONENTS IN THE MODULE. DO NOT TOUCH THE CONNECTOR PINS.ATTENTION – UNE DÉCHARGE ÉLECTROSTATIQUE PEUT ENDOMMAGERDES COMPOSANTS SEMI-CONDUCTEURS DANS LE MODULE. NE PASTOUCHEZ LE CONNECTEUR.Observe the following handling precautions: Wear an approved wrist-strap grounding device when handling the module Touch a grounded object or surface to rid yourself of any electrostatic discharged prior to handling themodule Handle the module from the bezel in front away from the connector. Never touch the connector pins. Do not install the module right next to an AC or high voltage DC module Route all the load voltage cables away from high voltage cablesDetailed Installation ProcedureDPage 11

Hardy 1734-WS Installation & Operation ManualThe base (A) mounts onto the DIN rail and provides the backplane. TheHI1734-WS POINT I/O module (B) snaps into the base. The removableterminal block (C) also snaps into the base and provides the wiring andterminations for field-side connections, as well as system power for thebackplane. For best performance, Hardy recommends use of 12-slotscrew-down terminal. Spring clamp blocks are only recommendedwhen using solid-core wiring.To remove, simply move the Clip (D) into the downward position andpull the HI1734-WS out of the base.For detailed installation instructions for the POINT I/O system, om/idc/groups/literature/documents/sg/1734-sg001 -en-p.pdfLoad Sensor ConnectionsThe HI 1734-WS weigh scale module will need to be connected toexternal sensors, whether a single load sensor connected directly, agroup of load sensors connected through a Junction Box or a platformscale such as a bench or floor scale connected direction. Each has itsown wiring configuration.Below are various connections for different types of sensors anddifferent POINT I/O Terminal Blocks.HI 1734-WS Weigh Scale Module Wire Terminations to Hardy Junction BoxesSCREW DOWN TERMINALS RECOMMENDEDPage 12

Hardy 1734-WS Installation & Operation ManualHI 1734-WS Weigh Scale Module Wire Terminations to Load SensorsSCREW DOWN TERMINALS RECOMMENDEDPage 13

Hardy 1734-WS Installation & Operation ManualPage 14

Hardy 1734-WS Installation & Operation ManualHI 1734-WS Weigh Scale Module Wire Terminations to Hardy Junction BoxesSCREW DOWN TERMINALS RECOMMENDEDPage 15

Hardy 1734-WS Installation & Operation ManualHI 1734-WS Weigh Scale Module Wire Terminations to Load SensorsSCREW DOWN TERMINALS RECOMMENDEDPage 16

Hardy 1734-WS Installation & Operation ManualNotes:1. If conduit is used, do not run load cell cable parallel to, or in the same conduit with power wiring,relay cable or other high energy cables.2. When four wire load sensors with C2, and four wire load sensors without C2, are directly connectedto the termination base assembly, wire jumpers must be installed in the termination base assemblywhere indicated.3. Required load cell cable for C2 electronic calibration system and INTEGRATED TECHNICIAN:Hardy Process Solutions part number C2Cable (6020-0001-0).Page 17

Hardy 1734-WS Installation & Operation Manual4. 12-position 1734-TOP3 and 1734-TB3 screw lock type termination base assemblies have the followingpins connected internally: Pin 4 to pin 8 Pin 5 to pin 9 Pin 6 to pin 10 Pin 7 to pin 115. With 8-position 1734-TOP and 1734-TB screw lock termination base assemblies, only use strandedwire when connecting multiple wires into a single terminal point.6. Termination base assembly screw lock wire size range: 14 AWG-22 AWG. Termination base assemblyscrew lock wire tightening torque: 7 lb-in [0.6nm] nominal.7. 8 position 1734-TOPS and 1734-TBS types, and 12 position 1734-TOP3S and 1734-TB3S type, springcage contact termination base assemblies may also be used, but are not recommended. If they areused, connect these termination base assembly types with 14 AWG to 22 AWG stranded wire.Page 18

Hardy 1734-WS Installation & Operation ManualChapter 4 – Setup and OperationChapter 4 covers the firmware and software settings used to prepare the module controller for calibration andoperation. The Setup procedures require Allen Bradley’s RS Logix 5000, Allen-Bradley RSLinx or RSLinx Lite.Power CheckTo make or change settings, there must be power to both the PLC and the module. Verify that the LED’s are lit fornormal operation. (See Figure Below)LED LightModule StatusStatusSolid GreenNormal (Running)Flashing GreenDevice on standby (needs commissioning)Solid RedUnrecoverable FaultFlashing RedMinor FaultFlashing Red/GreenDark - OffDevice Self testingNo power to the moduleLED LightNetwork StatusStatussolid GreenOn-line, connectedFlashing GreenOn-line, not connectedSolid RedCritical Link FailureFlashing RedConnection time-outFlashing Red/GreenDark - OffA specific communication faulted deviceNot Powered/Not OnlineScale StatusLED LightStatusSteady GreenRunning (Normal)Flashing GreenError No CalibrationSteady RedError Read Failure or Error Eeprom WriteFlashing RedRead Convert ErrorSetting Up Communications between the PLC and HI 1734-WSFollow these steps to set up communication between the ControlLogix PLC and the Weigh Scale Module. The stepsrequire that you have a new or open RS Logix 5000 project. For instructions, see your RS LOGIX 5000 manual.When not plugged directly into certain compatible controllers, the HI 1734 WS point I/O module requires acommunications adapter module. For this setup example/instructions, use the A-B 1734-AENT module.Page 19

Hardy 1734-WS Installation & Operation Manual In the program Controller Organizer, find the I/O Configuration Section.Right click on the Ethernet Module you will be installing the Point I/O under.Select ‘New Module’ to display a list of modules.From the Catalog list, select the 1734-AENT module. Configure the module by:o Enter a unique nameo Enter an IP address (Set up the addressing for the 1734-AENT module according to the instructionsin the Rockwell manual.)o In the module definition, set the chassis size to the correct size for the number of modules youhave, including the adapter module.oooPage 20Click OK to accept.Right click on the 1734-AENT module and select ‘New Module’.Select the HI 1734-WS (1-Channel Weigh Scale). This will add the new module under the AENTadapter module

Hardy 1734-WS Installation & Operation ManualThe module now shows in the controller Organizer in the I/O configuration under the Point I/O sectionRepeat the above steps for any additional modules.When setting up the HI 1734-WS module be sure to use an RPI (Requested Packet Interval) of 25 ms or greater (RPI 25 ms ) to avoid overloading the I/O adapters. For reference refer to Rockwell’s Point I/O specificationdocument.Page 21

Hardy 1734-WS Installation & Operation ManualConfiguration ParametersThe following parameters are parameters used in the Configuration of the IO:ConfigurationParametersGravity CorrectionPage 22Data TypeFLOATMotion ToleranceFLOATZero ToleranceFLOATTare WeightFLOATReference WeightFLOATSpan WeightFLOATAutoZeroToleranceFLOATEnable AutoZero TrackingINTUnitINTLoad Cell SensitivityINTWaverSaverNum AveragesINTINT

Hardy 1734-WS Installation & Operation ManualConfiguration with AOPUsing the AOP to configure the HI 1734-WS module makes it fast and easy. First, open the AOP and navigate toConfiguration. Make any required changes. Next, click on Apply. This will download the complete configurationtable to the module. Once the table has been downloaded the module is automatically configuredCommandsList of Hardy command NumbersPage 23Command NumberCommand0Read Parameter1Zero Cmd2Tare Cmd(0x64) 100 decCal Low Cmd(0x65) 101 decCal High Cmd(0x66) 102 decC2 Cal Cmd(0x80) 128 decIT Test(0x94) 148Set Default Parameters(0x0100) 256 decIT Test Reduce(0x0200) 512 decStability Test(0x1000) 4096 decWrite Cmd(0x10F0) 4336 decC2 Search

Hardy 1734-WS Installation & Operation Manual Page 240: READ PARAM CMD. To read a parameter, write a #0 to the CMD register (register #0), andwrite the parameter number in the ParameterID register of the output table. The parametervalue may then be read from ParameterValue register in the input table. This value may be ininteger or floating point format, depending on the parameter. The status register in the replywill contain the lower 16 bits of the system status word.o Status word bit 0: A/D erroro Status word bit 6 (0x40): Motion status.o Status word bit 7 (0x80): Not Found - the requested parameter number does notexist1: ZERO CMD. Write a 1 to the command register to ZERO the gross weight. The statusregister will read 0 if this command succeeds.o Status Error code 1 (Fail)o Status Error code 2 (ADC Failure)o Status Error code 3 (out of tolerance)o Status Error code 4 (motion)o Status code FF (cmd in progress)2: TARE CMD. Write a 2 to the command register to ZERO the net weight. The status registerwill read 0 if this command succeeds:o Status Error code 1 (Fail)o Status Error code 2 (ADC Failure)o Status Error code 4 (motion)o Status code FF (cmd in progress)0x64 (100 decimal): CAL LOW CMD. Write a 0x64 hex to the command register to performthe low step of a traditional calibration. The status register will read 0 if this commandsucceeds:o Status Error code 1 (Fail)o Status Error code 2 (ADC Failure)o Status Error code 4 (motion)o Status code FF (cmd in progress)0x65 (101decimal): CAL HIGH CMD. Write a 0x65 hex to the command register to performthe high step of a traditional calibration.o Status Error code 1 (Fail)o Status Error code 2 (ADC Failure)o Status Error code 4 (motion)o HardcalFailCounts 8: not enough counts between hard cal hi and hard cal loo Status code FF (cmd in progress)0x66 (102 decimal): C2 CAL CMD. Write a 0x66 hex to the command register to perform a C2calibration.o Status Error code 1 (Fail)o Status Error code 2 (ADC Failure)o Status Error code 4 (motion)o Status Error code 5 (no C2 cells)o Status Error code 6 (C2 capacities not equal)o Status Error code 7 (Non Hardy C2 load sensor)o Status code FF (cmd in progress)

Hardy 1734-WS Installation & Operation Manual 0x80 (128 decimal): IT test. Write a 0x80 hex to the command register to perform anIntegrated Technician test. (Requires an IT summing card.)o Status Error code 1 (Fail)o Status code FF (cmd in progress)0x94 (148 decimal): Set Default Parameters. Write a 0x94 to the command register to setall parameters and calibration back to def

Auto Zero Tracking Auto Zero Tracking automatically adjusts for zero weight. This capability allows the module to ignore material build-up in the weighing system within a pre-set auto zero tolerance. For auto zero to work, the current gross weight must be within the auto zero tolerance. The