Before choosing load cells for a specificapplication, the user shouldverifyit is possible to achieve sensible results from the planned weighing system. Itis not possible fora typical weighing system with a total capacity of 80,000 pounds to weigh in increments of 1 pound (1/80,000). Strain gauge load cells should not be expected to work beyond a minimum stable/repeatable weight increment of 1/10,000th of theload pointcapacity. With newer technology found in the HI4050, HI6300 sereis and HI6500 series this minimum has been expandedto 1:40,000.The final choice of load cells for your system will be somewhat of a compromise based on the standard capacities of Hardys load sensors and your application requirements. Hardy load sensors have outputs from0.9 to 3 Milli Volts per volt (mV/V). With 5 volts excitation, the full scale output for your Hardy load cell will be anywhere from0 Millivoltsto a maximum15 Millivolts. This output is the full scale output from no load to full capacity load. Full scale capacity takes into account the weight of any vessel or platform on the load cells, usually referred to as the Dead Load. This deadload will use upa portionof the load cell output, and as a result should be as low as possible compared to the Live Load (active weighing range). In practice this is not always easy to do, and it will depend on the overall resolution or accuracy required of your weighing system. If multiple load cells areconnected in parallel, then the total output will be thesummed average of the outputs from the individual load cells.When the range ofyour system has been calculated, this information can be related to electrical output in Millivolts (mV). This should then be related to the minimum weight increment or scale division which is required by the user.EXAMPLE:4 number of load cells (at 2 mV/V)75 kg capacity of each load cell300 kg total capacity of system (4 X 75 kg = 300 kg)5 VOLTS EXCITATION* 2 mV/V per load cell = 10 mV full scale output1mV = 30 kg (300 kg/10mV)100 kg dead load3.33mV Electrical output for dead load weight200 kg available live weight capacity applied equals6.66mV total electrical range for live weight, starting at a base of 3.33 mVUsing your specifications rather than the example above, you can determine the electrical output per division on your system and compare that to the specification of your Hardycontroller to ensure you are not expecting more than your system can deliver. If the signal is too low, then your system may need to be redesigned with respect to the live load weight and dead load, or load cell capacity.The calculation of load cell capacities for vessels will usually be different from thatof floor scales. It is unlikely that an individual load cell on a weigh vessel will be overloaded under normal working conditions (if calculations are correct). But on afloor scaleit is possible for one corner to carry a high percentage of any load cell placed on the weigh deck, so the calculation to determine correct capacity is doubled to prevent load cell damage. One method for determining the required load cell capacity for a particular application is outlined below:VESSEL/SCALE USING LOAD CELLSLoad cell capacity = (live weight + dead weight) / # of load cellsPLATFORM FLOOR SCALEScalecapacity = (live weight + dead weight)* 2

Hardy standard load cell capacities will then dictate which load cells should be used. When calculating capacities for platforms floor scales remember to double the normal capacity for safety. When calculating the capacity consideration must also be given to:a) Any adverse vibration within the system which may produce cyclic loading patterns on the cells. If using Hardy Instrument controllers you can use WAVERSAVER to reduce or eliminate the effects of vibration. This will not alleviate any over loading due to harmonic vibrations, just ignore the vibration.b) Unequal loading on the load cells due to fixed structures or irregular material distribution within the vessel or on the platform.c) Any mass that will be picked or dropped onto the scale with require a calculation of this additional force.NOTE: When calculating load cell capacity requirements the following guidelines may be useful: Advantage load cell series are certified to work at a 100% duty cycle at 100% of rated output. This means you can use thetotalratedcapacity and not worry about including overload protection by ordering oversized load cells. In some cases where the vessel does not expect large impact or uneven loading you can use 115% of the rated load cell capacity. This will reduce the overload protection but will function.

Please check with Hardy Tech Support and review any applications where you are considering 100% + loading.Generally it is safe to say thatmodern loadsensor ranges have been extended to show a duty cycle that covers the complete capacity.a) The live weight on any cell should fall between 20-100% of the capacity of the load cell.b) The dead load weighton any load cellcan fall between 1-70% of the capacity of the load cell.

For platform scales the capacity is usually twice what you would normally expect, because forklifts regularly drive over the platform scale, and if the capacity was not doubledthe scalewould be damaged due to overloading.If you need additional information please click on the "Ask A Question" tab using Hardy's online WebTech knowledgebase. If you need on-site assistance call Hardy Technical Support at 800-821-5831 option #4 or 858-278-2900 option #4. We offer Local Field Service in the continental U.S. and Canada for system installation, startup, inspection, verification, calibration and certification, emergency troubleshooting, on-site training and routine preventative maintenance for your Process Weighing instrumentation (even for non-Hardy equipment). We can have someone at your facility when you need us!Hardy Tech Support is always looking to improve service to our customers. Please help us provide you better service by rating this answer. We appreciate your feedback!

DISCLAIMER: This knowledge base web site is provided as a service to our customers and not intended to be an exhaustive or comprehensive treatment of the subject or subjects. The information in this web site does not constitute application, design, or other professional engineering advice or services. Prior to making any decision or taking any action that could affect your machinery or equipment, we suggest you consult a qualified professional. HARDY PROCESS SOLUTIONS DOES NOT GUARRANTEE THE COMPLETENESS, TIMELINESS OR ACCURACY OF ANY DATA CONTAINED IN THIS WEB SITE AND MAKES CHANGES TO IT FROM TIME TO TIME AT ITS SOLE DISCRETION AND WITHOUT NOTICE. ALL INFORMATION CONTAINED HEREIN IS PROVIDED TO OUR CUSTOMERS ON AN "AS IS" BASIS AND IN NO EVENT WILL HARDY PROCESS SOLUTIONS BE LIABLE FOR ANY DAMAGES OF ANY KIND INCLUDING CONSEQUENTIAL, LOSS PROFIT OR PHYSICAL DAMAGE, EVEN IF HARDY PROCESS SOLUTIONS HAS BEEN NOTIFIED ABOUT THE POSSIBILITY OF SUCH DAMAGES. HARDY PROCESS SOLUTIONS TAKES NO RESPONSIBILITY FOR ANY WARRANTIES WHETHER EXPRESSED OR IMPLIED IN RESPECT OF THE INFORMATION (INCLUDING SOFTWARE) PROVIDED HEREIN, INCLUDING IMPLIED WARRANTIES OF APPLIBILITY FOR A SPECIFIC PURPOSE, MERCHANTABILITY, AND NON-INFRINGEMENT.

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If Hardy does not have the right capacity load cell, what should I do?

Answer ID 149 | Published 02/06/2002 07:07 AM | Updated 02/03/2014 10:40 AM

Hardy does not have a 5,000 pound load point. What load point should I use when a 5KLB load cell is required?

The Advantage Load Points have two parameters you must understand to make your selection. The parameters are "Operational Overload" and "Safe Overload". The "Operational Overload" of the Advantage Load Points is 150% of rated capacity. This means the HI HLPS4.5K load point can be used for loads up to5175 pounds by reducing the "Safe Overload"window to 115%. The "Safe Overload" is the maximum weight the load cell can support without being damaged. If the vessel in question does not support a large agitator or is not subjected to large impact loads, it could be recommended that the HI HLPS4.5K Advantage Load Points may be used when a 5K load cell is requested.Fora normal system with agitators, seismic activities,and live bottoms, the total dead and live loadshould not exceed 100% of the capacity of the load cells. Four 4.5K load cells equal 18,000 lb total recommended capacity. Many times designers recommend a capacity buffer to ensure there is not going to be any damage to the load cell as it approaches maximum load capacity. This is an out dated idea and the modern Advantage is fully capable of being used at the 100% level and not show any signs of damage.Verify the total scale loading and if there was any fudge factor placed on the total capacity number. You maybe able to use a smaller capacity andrealize a better weight resolution.

Seismic requirements may require a higher capacity than just the deadload and liveload calculations. Alwaysrefer this type of questiona qualified mechanical engineer.Additional or structural reinforcement or capacity maybe required to meet seismic conditions for your vessel.If you need additional information please click on the "Ask A Question" tab using Hardy's online WebTech knowledgebase. If you need on-site assistance call Hardy Technical Support at 800-821-5831 option #4 or 858-278-2900 option #4. We offer Local Field Service in the continental U.S. and Canada for system installation, startup, inspection, verification, calibration and certification, emergency troubleshooting, on-site training and routine preventative maintenance for your Process Weighing instrumentation (even for non-Hardy equipment). We can have someone at your facility when you need us!

Hardy Tech Support is always looking to improve service to our customers. Please help us provide you better service by rating this answer. We appreciate your feedback!

How can I tell if my load cell is good without using Integrated Technician?

Answer ID 612 | Published 02/17/2003 12:10 PM | Updated 03/11/2014 05:26 PM

I am using older load cells from Hardy Process Solutions (or from another company) and I want to make sure they are functioning properly before I use them in another application. I don't have the Hardy feature "Integrated Technician" in my junction box or controller, so I checked the installation/troubleshooting guide which says to check the resistance between the signal wires and the excitation wires and the resistance of each should be around 350 ohms. Well, the resistance between the signal wires on all 8 load cells was right at 350 ohms, but the resistance between the excitation wires on all 8 load cells was around 387 ohms. So, are all of these load cells bad, or is it ok for the excitation resistance to be 387 ohms?

The true test of a load cell is the load cell's signal millivolt output at no load, mid rangeand full load. Attached is a tech note on load cell troubleshooting that should answer your question.There are troubleshooting guides in chapter eight of the individual weight controller manuals. There are also other articles available in Hardy WebTech Knowledge base that addresses other methods to determine the health of your scale system.

Using information provided or derived from different sources can provide readings and assumptions that can determine the health of your weighing system.For this example we will use:3 Load cells with capacities of 1000 lb each. Full scale output (FSO) readings for each load cell (acquired from load cell certificates) for our example are:#1= 3.0003 Mv/V#2= 3.0034 Mv/V#3= 2.9994 mV/VMillie volt reading at empty = 5 mVExcitation voltage = 5 VDC1. Adding the individual load cell weight capacities (lb or kg) will determine the scale system's rated capacity (3000 lb in this example)2. Average the full scale output of each load cell to determine the scale's mV/V output at rated capacity. (3.0010 in this example)3. Multiple the Excitation voltage by the average mV/V to determine the milli-volt output at rated system capacity. (5.00 V x 3.0010 mV/V = 15.0050 mV @ 3000 lb in this example)4. Measure the empty vessels load cell output at the signal + and signal - terminals. (2.25 mV in this example)5. To determine the amount of load cell capacity used by the empty vessel, dead load, divide the scale system's rated capacity (lb/kg) by the milli-volt output at rated system capacity (found in step 3) Multiple this finding by the milli-volt reading of the empty vessel (found in step 4) (3000/15.0050 x 2.25 = 449.85 lb dead load in this example)6. A secondary calculation gives the live load of the scale system. (Dead load - scale capacity 449.85 - 3000 = 2500.15 system live load)7. A general test could be performed by adding a known weight to the scale and measuring the mV signal output increase. This would give a general indication if the scale is linear. Mv readings to the second decimal place would be sufficient for this test. Adding 450 lbs to our test scale should result in a signal reading of 4.50 mV.8. Divide the mV@FSO by the rated scale capacity lb = mV/(lb) times the test weight, plus the original mV reading at empty should equal 4.50 mV. (15.0050 mV/3000 lb x 450 lb + 2.25 = 4.50 mV in this example)

9. Knowing the capacity of the load cells, excitation voltage, and a known weight the average mV/V rating of the load cells can be determined.10. A 450 lb test weight increased the Mv reading by 2.25 mV in this example. (A 2.25 Mv increase / 450 lb x 3000 lb scale capacity / 5 v EXC = 3 Mv/V)For this example itwas determined the load cellswere 3 Mv/V with an accuracy of two decimal points. Most meters are OK to two decimal points on the Milli-volt scale. More decimal points than two require a high quality meter with a recent calibration sticker.If you need additional information please click on the "Ask A Question" tab using Hardy's online WebTech knowledgebase. If you need on-site assistance call Hardy Technical Support at 800-821-5831 option #4 or 858-278-2900 option #4. We offer Local Field Service in the continental U.S. and Canada for system installation, startup, inspection, verification, calibration and certification, emergency troubleshooting, on-site training and routine preventative maintenance for your Process Weighing instrumentation (even for non-Hardy equipment). We can have someone at your facility when you need us!

Hardy Tech Support is always looking to improve service to our customers. Please help us provide you better service by rating this answer. We appreciate your feedback!