‫LAUMAS responds

‫In this section we have collected some answers to the questions we receive most often. Before requesting direct assistance please kindly check that your question has not already been reported and solved in this section.

SUPPORT (9)

1. I'm an end user, who should I contact to purchase LAUMAS products or to receive technical assistance?

LAUMAS has a network of authorized dealers and technical assistance centres all over the world.

Consult the sales network section to find out which is the closest dealer or technical assistance centre.
To ask for information fill out the form.

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2. Can you come and install and calibrate my weighing system?

LAUMAS does not provide this service directly, but uses a network of technical assistance centers around the world.

See the map in the sales network section to find out which one is closest to you.
To ask us for information please fill out the form.

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3. Why does the weight indicator always give me a negative weight value?

The cause could be:

  • ELECTRICAL
  • MECHANICAL

Electrical cause: you may have reversed the polarity of the signal or power supply conductors of the load cell.
Solution: check the connections by comparing the load cell data sheet with the wiring diagram in the instrument manual.

Mechanical cause: you may have reversed the direction of load of the load cell.
Solution: check the direction of load that delineates the direction in which the load cell has to work. You can find it indicated on the load cell by an arrow.

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4. Why does the weight indicator give me an incorrect value when I load a known weight?

This is the most common case of a malfunction in a weighing system and could be due to a calibration error or a mechanical problem.

Here are the tests you can run to identify the problem and find the solution:

  • Load several weights that are proportional to each other and check whether the error is constant.

    For example: if you load 50 kg on the scale and the indicator gives you a value of 55 kg, try unloading it and reloading it first with 100 kg and then with 200 kg.
    If the error stays proportional, i.e. instead of 100 kg the indicator shows 110 kg and instead of 200 kg it shows 220 kg, it means that the system does not have a mechanical problem.

    In this case, simply perform the calibration again, following the procedures in the manual.

  • If, on the other hand, the error displayed is random, so not proportional, then the problem is mechanical or it regards assembly.

    Immediately verify the mechanical installation of the load cells, mounting accessories and structural components (e.g. pipes, silo legs, cylinders, etc.).

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5. Why does the weight indicator not return exactly to 0 when I remove the load?

The problem may be mechanical or regard assembly. Immediately verify the mechanical installation of the load cells, mounting accessories and structural components (e.g. pipes, silo legs, cylinders, etc.).

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6. Why does moving the load to another point on the scale change the value displayed on the weight indicator?

The problem may be mechanical or regard assembly. Immediately verify the mechanical installation of the load cells, mounting accessories and structural components (e.g. pipes, silo legs, cylinders, etc.).

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7. If I leave the weight indicator off for a long time and the buffer battery runs out, are the calibration data and batching constants lost?

No. If the battery goes dead, the only data that are lost are the date and time, which will then have to be reprogrammed.

All the remaining parameters are stored in non-volatile memory.

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8. How do I open a technical support ticket?

After logging in, select the Menu SUPPORT AND DOWNLOADS > SUPPORT > Technical Support Ticket > New Ticket.

The service is free and reserved for users with full Registration on the website.

Are you a new user? Request full registration.

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9. Besides technical support, what can I request with a ticket?

In addition to technical support, you can open a ticket to request:

  • Returns for repairs/reworking (RMA);
  • Spare parts;
  • Duplicate test certificates.

The service is free and reserved for customers with full registration.

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LOAD CELLS (4)

1. How can the proper functioning of a load cell be verified?

To verify the correct operation of one or more load cells, tests should be performed using a digital multimeter with mV range. The test must be performed by qualified personnel able to perform the measurements accurately. We can see in detail the tests to be performed: 

Load cells resistance measure by means of digital multimeter:

  • Disconnect the load cells from the instrument and check that there is no moisture in the cell junction box caused by condensation or water infiltration. If so, keep cleaning the system or replace it, if necessary.
  • The value between the positive signal wire and the negative signal wire must be equal or similar to the one indicated in the load cell data sheet (output resistance).
  • The value between the positive excitation wire and the negative excitation wire must be equal or similar to the one indicated in the load cell data sheet (input resistance).
  • The insulation value between the shield and any other cell wire and between any other cell wire and the body of the load cell must be higher than 20 Mohm (mega ohms).

Load cells voltage measure by means of digital multimeter:

  • Take out the load cell to be tested from underneath the container, or alternatively, lift the container support.
  • Make sure that the excitation of two wires of the load cell connected to the instrument (or amplifier) is 5 Vdc +/- 3% (10Vdc +/-3% for instruments series TPS- TPZ).
  • Measure the response signal between the positive and the negative signal wires by directly connecting them to the multimeter, and make sure that it is comprised between 0 and +/- 0.5 mV (thousandths of a Volt).
  • Apply load to the cell and make sure that there is a signal increment.

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2. Are LAUMAS load cells compatible with any instrument of any brand and vice versa?

Yes, all our load cells are compatible with weight indicators and transmitters from any manufacturer, which have mV / V input for strain gauge sensors.

On the other hand, all of our weight indicators are compatible with strain gauge cells from any manufacturer.

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3. What difference is there between a 4-wire and a 6-wire load cell? What needs to be taken into account when installing them?

The 6-wire load cells have two extra wires called “reference” (Sense + and Sense –) that are used to measure and adjust the actual voltage reaching the load cells.

Thanks to the references, the 6-wire load cells can compensate for a voltage drop, e.g. due to temperature changes or cable length, without affecting weight measurement.
For this reason, if necessary, their cable can be shortened without damaging the load cell, while bearing in mind that making a modification to the original product involves the loss of the warranty.

The 4-wire load cells, on the other hand, are calibrated and thermally compensated in relation to the length of the cable with which they are supplied as standard.

That is why we recommend that you never shorten the cable: this could compromise the reliability of the calibration and compensation.
In addition, in order to limit a voltage drop in the portion of the cable between the junction box and the weight indicator, it is recommended to use a shielded cable with a significant cross-section (at least 1 mm2).

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4. Do you have UL certified load cells?

No, because UL certification for a load cell is not necessary.

UL regulations refer to the safety of electronic instruments. The mark indicates that the instrument has been tested to ensure that the user does not get electrocuted or receive an electric shock.

However, UL considers load cells to be an ultra-low voltage device (less than 50 VAC or 75 VDC) with very low current, so the risk of electrocution is de facto non-existent.

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ELECTRONIC INSTRUMENTATION (6)

1. Which programs/firmware can be installed on the W Series weight indicators?

You can choose from several programs:

  • BASE: program to manage setpoints, without any specific batching functions.

  • LOAD: single-product load batching program with 99 formulas.

  • UNLOAD: single-product unload batching program with 99 formulas.

  • 3/6/14 PRODUCTS: load batching programs for up to 3, 6 or 14 products with 99 formulas.
    The RELE6PROD external relay module is required for the 6-product program.
    Both the RELE6PROD external relay module and the RELE14PROD external relay module are required for the 14-product program.

  • RIP: serial remote display program with setpoint, without any batching functions.

  • MULTI: firmware that includes all the previous programs that the installer can select on his own. Ideal for products that need to be stocked and whose final application is not yet known.

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2. What are the advantages of LAUMAS weight indicators with MULTI (multiprogram) software for dealers and installers?

With a weight indicator equipped with a MULTI program, the installer can independently select the type of software desired, in order to meet multiple needs.

Consequently, the dealer who decides to have this type of indicators in stock will have available “wildcard” instruments capable of adapting to the different supply needs that may arise.

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3. Is it possible to view the weight measured by a load cell system on two different instruments?

Yes, with the W-series weight indicators you can view the weight on two different instruments and manage the weighing system from two separate locations using the weight reading mode via serial port.

Simply connect one of the two weight indicators to the load cells and transfer the measured weight to the other weight indicator, via port RS232 or port RS485.
In this way, the second weight indicator becomes independent, as if it were also connected directly to the load cell system.

The procedure to enable this function is described in the “Reading the weight via the serial port” section in each instrument’s manual.

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4. Is it possible to calibrate an instrument without having sample weights available?

Yes, all W-series weight indicators and LAUMAS weight transmitters have a theoretical calibration procedure that allows calibration to be carried out by simply setting the load cell data in the instrument's menu.

You can watch how to calibrate a LAUMAS instrument in the tutorial: Calibrating weight indicators and weight transmitters.

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6. Is there software to configure and manage LAUMAS electronic instrumentation from a PC?

Yes, almost all LAUMAS weight indicators and weight transmitters can be managed from a PC via the free Instrument Manager software.

The software makes it possible to configure parameters, monitor, perform true calibration and update our instruments.
Read more about Instrument Manager and download it for free.

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INSTALLATION (11)

1. What are the rules to follow for correctly installing load cells?

Check that the load cell supporting surfaces are parallel and usually flat.

Use suitable mounting accessories to compensate if any of the support surfaces are slightly out of parallel.

The supporting surfaces must be sufficiently rigid and in theory non-deformable.

For load shear beam, bending beam and single point cells, the support value indicated on the datasheet must be respected.

Pay attention to the direction of load indicated on the datasheet or on the cell body: this must be oriented in the same direction as the force being applied.

For safety reasons, it is advisable to use the load cells at a maximum of 70-80% of their nominal capacity.
In the case of weighing of structures with 4 supports, keep in mind that the load will not be evenly distributed on them and that 85-90% of the applied load will be spread across just 3 supports.




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2. What are the peculiarities of single point / platform load cells?

The single point and platform load cells are able to weigh correctly within an area specified on the datasheet.
For example, using a cell guaranteed for an area of 400 by 400 millimetres, we are certain that, by applying a weight force at any point of a structure of such dimensions, the weight detected will be correct.
By installing a structure of larger dimensions than those indicated on the datasheet or by applying an object that protrudes out of the structure, the single point load cells may be damaged and in any case an incorrect weight value is obtained.




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3. When installing a load cell or load cell system, how can friction that could compromise weighing accuracy be limited?

A weighing system is all the more precise when the weighed structure is free of friction. When there are pipes, before anchoring the pipe to the weighed structure, check that it is close to and in line with the nozzle to which it will be attached.

Friction can be limited by using flexible hoses and elastic joints or free inlets with rubber protection, such as of the bellows type.

Alternatively, position the first anchor bracket in the horizontal section as far away as possible from the structure being weighed, at least 40 times the diameter of the pipe.




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4. How to check if a load cell has been installed correctly?

To check the correct mechanical installation of the weighing system, reset the weight indicator and apply a force to the system, then remove it. The indicator should return perfectly to zero.

In the case of a weighing system with multiple load cells repeat this operation for each cell. At system loading the weight values will be similar on each cell, at system unloading they will indicate zero.




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5. How to install multiple load cells connected in parallel correctly?

To connect multiple load cells in parallel, use a watertight junction box, with a suitable terminal strip, or a multi-channel transmitter in the box.

The cables in and out of the box or multi-channel transmitter require the installation of cable clamps.




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6. What characteristics must the extension cables used for the connection between the junction box and the weight indicator/weight transmitter have?

The extension cables used for the connection must be shielded. We recommend using a 6-wire cable with reference/sense management, which can compensate for the voltage drop due to the distance between the devices. If possible, it should be inserted into the cable duct by itself and laid as far away as possible from the power cables.

When using 4-conductor connection cables, use a minimum cross-section of 1 square millimetre and preferably not more than 300 metres in length.




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7. What should I do if I need to weld with load cells that have already been installed?

Do not weld with load cells already in place. If this becomes unavoidable, position the welding machine's mass clamp as close as possible to the point where the welding is to be carried out, so as to avoid current passing through the body of the cell and damaging it.




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8. In weighing systems with multiple load cells, how should constraints and accessories be created and positioned to counteract lateral forces and the danger of tipping over due to possible shocks, vibrations, wind forces, earthquakes, etc.?

We offer a variety of mounting accessories. Their purpose is to ensure the correct application of the load cell and maximum reliability and precision and compatibility with the mechanical, electrical and pneumatic connections present on the structure being weighed.

In multi-cell systems we recommend positioning the restraints so that they are able to withstand any lateral forces.

The system designer will have to assess whether the standard mounting accessories are sufficient for the purpose, or whether additional measures should be taken depending on: shocks and vibrations, wind thrust, seismic classification of the installation area, consistency of the supporting base.

Providing constraints that can counteract horizontal forces allows the load cells to work correctly, thus avoiding potentially damaging stresses.

The provision of anti-tip constraints is advised for weighing systems on silos, tanks or structures that are located outdoors and subject to potential wind thrust, earthquakes, accidental impacts with operating machines and other similar situations.




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9. How can a correct earthing system be implemented to prevent electrostatic charges from passing through and damaging the load cells?

Electrostatic charges have the potential to damage the load cells. For this reason, we recommend that you connect the top plate of each cell to the bottom plate of each cell using a copper conductor of suitable cross-section. Then, connect all the lower plates to each other and connect them to the same grounding network.

This allows electrostatic charges to be discharged to the ground without passing through and damaging the load cells.

A correctly grounded system removes the possibility of future damage to the cells and the instrument connected to them.

Extending the earthing system through the metal parts of the structure being weighedis absolutely forbidden.




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10. What are the standards that must be followed for the correct installation of electronic instrumentation (weight indicators, weight transmitters, weighing and batching instruments)?

The load cell cable must be self-contained and must not pass through cable ducts with other cables. We recommend that you connect it directly to the weight indicator or transmitter without interruptions and without terminal blocks.

We also recommend that you do not install the electronic instrumentation in a cabinet containing an inverter. If unavoidable, install special filters and separators between the inverters. The person in charge of the electrical control panel must prepare and install all the electrical protections necessary for the system.

We recommend that you always keep the equipment powered to prevent condensation forming.




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11. What is important to check if the weighing system is to be applied on leg structures or on silos and tanks?

If the weighing system is being used on leg structures or silos, always check that the supports are connected to each other; if not, connect them appropriately.




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STANDARDS AND DIRECTIVES (4)

1. My company is ISO 9001 certified and I use a scale for my production. What should I do to manage it according to the standard?

In this case, the weighing instruments must be calibrated on a periodic basis that is established by the company in agreement with the Quality Inspector, also depending on the intended use.

If the instrument plays a fundamental role in the company production process and the frequency of its use is high, the checks can be monthly or half-yearly.

If, on the other hand, the instrument is used for marginal activities and with low frequency, the checks may be more extended over time, for example every 24 - 36 months.

The verification is carried out using calibrated sample weights, referable to national or international samples.

LAUMAS has a worldwide network of service centres capable of carrying out calibration reports that can be used in an ISO 9001 system.
For information on the closest service centre, fill out the form.

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2. What are approved weighing systems (or systems for legal for trade use) in compliance with NAWI 2014/31/EU?

A non-automatic weighing instrument (NAWI) is an instrument that requires the intervention of an operator during the weighing process.

European Directive 2014/31/EU requires the use of non-automatic weighing instruments complying with the Directive for the following use categories:

  • commercial transactions;
  • calculation of tolls, tariffs, taxes, premiums, fines, remuneration, allowances or similar types of fee;
  • application of provisions laid down by law, regulations or provisions for legal opinions;
  • monitoring, diagnosis and care of patients in medical practice;
  • making prescription medicines in a pharmacy and tests carried out in medical and pharmaceutical laboratories;
  • determination of the price for direct sales to the public and the packaging of prefabricated packing.

Before being put into service, instruments for legal for trade use must undergo a conformity assessment and other periodic checks over time.
The checks are carried out every three years for Italy, while for the other Member States of the European Union the frequency is determined by the single national laws.

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3. Where can I perform the conformity assessment (first check) or periodic check on my NAWI weighing instrument?

We can carry out the first check for NAWI (CE-M) on LAUMAS weighing instruments both at our headquarters and on site through our network of support centers, in accordance with Directive 2014/31/EU.
According to this Directive, conformity assessment is necessary if the weighing system is used in applications for legal for trade use or for medical, pharmaceutical, judicial or sanctioning purposes (see FAQ No.21).

For subsequent checks (periodic checks), it is necessary to contact an accredited bodyin the area.
In Italy, the periodic checks are carried out every three years starting from the date of conformity assessment, while for the other Member States of the European Union the frequency is determined by the single national laws.

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4. What are Automatic Weighing Instruments (AWI) compliant with Directive 2014/32/EU, or the Measuring Instruments Directive (MID)?

An automatic weighing instrument is an instrument that determines the mass of a product without the intervention of an operator.
Its characteristic is to follow a predetermined program of automatic processes.

For commercial use, such instruments must comply with the requirements stated in Directive 2014/32/EU, in particular:

  • The essential requirements of Annex I ;
  • The specific requirements of Annex VIII (MI-006).

LAUMAS provides weight indicators (W series) and weight transmitters (TLB and TLB4) that comply with the Directive and are certified as “MID transmitters” for gravimetric filling machines (TLB4 also for catchweighers). In order to compose a weighing system certified as a complete MID device, the weight transmitters will have to be connected to other devices and the whole assembly will have to be certified.

Here is a list of the main automatic weighing instruments that must meet the OIML (International Organization of Legal Metrology) requirements and recommendations:

  • Catchweigher - OIML R 51
    An automatic instrument for determining the mass of discrete loads (i.e. composed of a single piece that cannot be divided, such as a package) or single loads of bulk material.

  • Control weight batcher - OIML R 51
    A catchweigher that divides objects of different masses into one or more subsets, based on how much their mass differs from a nominal target value that you would like to obtain.

  • Weight labeler - OIML R 51
    A catchweigher that labels individual items with their weight.

  • Weight/price labeler - OIML R 51
    An automatic instrument that labels individual items with their weight and price information.

  • Gravimetric filling machine - OIML R 61
    An automatic instrument that fills containers with a predetermined and virtually constant mass of bulk product.

  • Discontinuous totalizer (hopper totalizer) - OIML R 107
    An automatic instrument that determines the mass of a bulk product by dividing it into separate loads.
    The masses of each discrete load are determined one after another and added together. Each discrete load is then added to the heap.

  • Continuous totalizer - OIML R 50
    An automatic instrument that determines the mass of a bulk product placed on a conveyor belt, without the need for a systematic subdivision of the product and without interrupting the movement of the belt.

  • Railway vehicle weighbridge - OIML R 106
    An automatic instrument equipped with a load receiver including tracks, on which transit the railway vehicles being weighed.

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DOWNLOAD (6)

1. I need technical documentation in multiple languages. Where and how can I find it?

From the PRODUCTS menu, select the product whose documentation you are looking for.

On the dedicated web page, in the DOWNLOAD section there are flags through which you can check which documents are available in the different languages.

Click on your language to have access to all the available documentation for the selected product.

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2. Where can I download product manuals?

To download a manual you must first be registered on the website, with quick or full registration: you can do it here.

After logging in, select the Menu SUPPORT AND DOWNLOADS > DOWNLOADS > Manuals and Data Sheets.

On this page you can search for and download manuals and data sheets for all our products.

Alternatively, from the PRODUCTS menu, select the product whose documentation you are looking for.
You will also find reference manuals on the dedicated web page in the DOWNLOADS section.

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3. Where can I download software and configuration files?

To download software or a configuration file you must first be registered on the website, with quick or full Registration: you can do it here.

After logging in, select the Menu SUPPORT AND DOWNLOADS > DOWNLOADS > Software and configuration files.

On this page you can search for and download the software/configuration files of the instruments that require them, as well as the Instrument Manager supervision software.

Alternatively, from the PRODUCTS Menu > ELECTRONIC INSTRUMENTATION, select the instrument you are interested in.
You will also find the reference configuration file on the dedicated web page in the DOWNLOADS section.

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4. Where can I download product CAD drawings?

To download a product’s CAD drawing you must first be registered on the website, with quick or full Registration: you can do it here.

After logging in, select the Menu SUPPORT AND DOWNLOADS > DOWNLOADS > CAD Drawings.

On this page you can search for and download all the available CAD drawings for our products.

Alternatively, from the PRODUCTS Menu, select the product whose drawing you are looking for. If available, you will find it in the DOWNLOADS section of the dedicated web page.

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5. Where can I find the test certificates for the load cells and/or weight transmitters and weight indicators I have purchased?

Test certificates are always provided together with the products purchased.
If you need a duplicate, you can request it by opening the specific support ticket.

After logging into the website, from the SUPPORT AND DOWNLOADS Menu, under the SUPPORT category, select Test certificates duplicate and fill in the Ticket.

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6. Where can I download the various product certificates?

To download a product certificate (metrological certifications, certifications for areas with an explosion hazard or other certifications) you must first be registered on the website, with quick or full Registration: you can do it here.

After logging in, select the Menu SUPPORT AND DOWNLOADS > DOWNLOADS > Certificates.

On this page you can search for and download all the available certificates for our products.

Alternatively, from the PRODUCTS Menu, select the product whose certificate you are looking for. You will find it in the DOWNLOADS section of the dedicated web page

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INSIGHTS (3)

1. What is a load cell?

A load cell is an electronic component (transducer) to which a weight force is applied.

The load cell is able to convert the weight force applied into an electrical signal in mV proportional to the mechanical deformation expressed in tenths of a millimetre caused by the same force.

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2. What is the principle of operation of a load cell?

load cell consists of a metal body (stainless steel or aluminium) to which strain gauges are applied. The strain gauges are constituted by a grid of thin metal wire (constantan) applied to a support of insulating material and glued into specific areas of the load cell. The strain gauges follow the deformations of the surface of the load cell to which they are bonded, lengthening and shortening along with it; these dimensional changes cause a variation in electrical resistance, which through the "Wheatstone Bridge" connection, is converted into a proportional electric signal normally expressed in mV (thousandths of a volt).

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3. What types of load cell are available on the market?

Depending on the type of application for which they have been built, or the construction method used, we mention some common types of load cells that LAUMAS can offer you:

  • single point/off-center/for platforms - placed at the centre of a plane surface, they are capable of correctly weighing the weight force applied at any point, they are normally employed in all single cell platforms and scales
  • low profile compression - robust and easy to install, together with the corresponding weigh module suitable for weighing silos, tanks, hoppers, mixers and reactors even with large scale
  • column compression - typically used in weighbridges or with related weigh modules for silos of additional capacity, even installed outside
  • compression and tension - for material testing machines, special tests, etc.
  • tension - for creating suspended weighing systems, batching plants or to be applied on tie rods to transform old mechanical scales into electronic scales
  • shear beam - cells commonly used in platforms suitable for weighing small and medium-sized silos and transport systems with belts, rollers, etc.
  • double shear beam - typically used in weighbridges or with related weigh modules for silos of additional capacity, even installed outside
  • bending - cells commonly used for small-scale weighing systems with dosing machines and weight bagging and filling systems, bagging machines, filling machines, etc.
  • pin - applied in lifting systems on ropes or pulleys and custom made according to the customer's specifications
  • anchor - normally applied to monitor the tensioning force of tie rods present in civil works, dams, bridges, tunnels, etc.
  • pre-amplified - cells with an internal amplifier that allows a pre-amplified analogue output 0-10V – 4-20mA

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