FAQ

For convenience, terms which are defined in this standard are printed in UPPER CASE when used in the definition of another term.

AMBIENT TEMPERATURE – The temperature of the medium surrounding the LOAD CELL.

AXIAL LOAD – A load applied along the PRIMARY AXIS.

BAROMETRIC SENSITIVITY – The change in ZERO BALANCE due to a change in ambient barometric pressure. Normally expressed in units of %RO/atm.

CALIBRATION – The comparison of LOAD CELL OUTPUT against standard test loads.

CAPACITY – The maximum AXIAL LOAD a LOAD CELL is designed to measure within its specifications.

COMBINED ERROR – The maximum deviation of the CALIBRATION curve from the straight line drawn between MINIMUM LOAD OUTPUT and MAXIMUM LOAD OUTPUT, normally expressed in units of %FS. Both ascending and descending curves are considered.

CREEP – The change in LOAD CELL SIGNAL occurring with time while under load and with all environmental conditions and other variables remaining constant. Normally expressed in units of % of applied load over a specified time interval. It is common for characterization to be measured with a constant load at or near CAPACITY.

CREEP RECOVERY – The change in LOAD CELL SIGNAL occurring with time immediately after removal of a load which had been applied for a specified time interval, environmental conditions and other variables remaining constant during the loaded and unloaded intervals. Normally expressed in units of % of applied load over a specified time interval. Normally the applied interval and the recovery interval are equal. It is common for characterization to be measured with a constant load at or near CAPACITY.

CREEP RETURN – The difference between LOAD CELL SIGNAL immediately after removal of a load which had been applied for a specified time interval, environmental conditions and other variables remaining constant during the loaded interval, and the SIGNAL before application of the load. Normally expressed in units of % of applied load over a specified time interval. It is common for characterization to be measured with a constant load at or near CAPACITY.

DEFLECTION – The displacement of the point of AXIAL LOAD application in the PRIMARY AXIS between the MDL and MDL+CAPACITY load conditions.

ECCENTRIC LOAD – Any load applied parallel to but not concentric with the PRIMARY AXIS.

FULL SCALE or FS – The OUTPUT corresponding to MAXIMUM LOAD in any specific test or application.

HYSTERESIS – The algebraic difference between OUTPUT at a given load descending from MAXIMUM LOAD and OUTPUT at the same load ascending from MINIMUM LOAD. Normally expressed in units of %FS. It is common for characterization to be measured at 40-60% FS.

INPUT RESISTANCE – The resistance of the LOAD CELL circuit measured at the excitation terminals with no load applied and with the output terminals open-circuited.

INSULATION RESISTANCE – The DC resistance measured between the bridge circuit and the case. Normally measured at 50 VDC.

LOAD CELL – A device which produces an OUTPUT proportional to an applied force load.

MAXIMUM AXIAL LOAD, SAFE – The maximum AXIAL LOAD which can be applied without producing a permanent shift in performance characteristics beyond those specified. Normally expressed in units of % CAPACITY.

MAXIMUM LOAD – The highest load in a specific test or application, which may be any load up to and including CAPACITY +MINIMUM LOAD, but may not exceed CAPACITY significantly.

MAXIMUM AXIAL LOAD, ULTIMATE – The maximum AXIAL LOAD which can be applied without producing a structural failure. Normally expressed in units of % CAPACITY.

MAXIMUM LOAD AXIS MOMENT, SAFE – The maximum moment with respect to the PRIMARY AXIS which can be applied without producing a permanent shift in performance characteristics beyond those specified.

MAXIMUM MOUNTING TORQUE, SAFE – The maximum torque which can be applied concentric with the primary axis without producing a permanent shift in performance characteristics beyond those specified.

MAXIMUM SIDE LOAD, SAFE – The maximum SIDE LOAD which can be applied without producing a permanent shift in performance characteristics beyond those specified.

MEASURING RANGE – The difference between MAXIMUM LOAD and MINIMUM LOAD in a specific test or application. It may not exceed CAPACITY.

MINIMUM DEAD LOAD or MDL – The smallest load for which specified performance will be met. It is normally equal to or near NO LOAD in single mode applications and is of necessity equal to NO LOAD in double mode applications.

MINIMUM LOAD – The lowest load in a specific test or application, differing from NO LOAD by the weight of fixtures and load receptors which are attached plus any intentional pre-load which is applied.

MODE – The direction of load. Tension and Compression are each one mode.

NATURAL FREQUENCY – The frequency of free oscillations under conditions of NO LOAD.

NO LOAD – The condition of the LOAD CELL when in its normal physical orientation, with no force input applied, and with no fixtures or load receptors attached.

NONLINEARITY – The algebraic difference between OUTPUT at a specific load and the corresponding point on the straight line drawn between MINIMUM LOAD and MAXIMUM LOAD. Normally expressed in units of %FS. It is common for characterization to be measured at 40-60 %FS.

NONREPEATABILITY – The maximum difference between OUTPUT readings for repeated loadings under identical loading and environmental conditions. Normally expressed in units of %RO.

OUTPUT – The algebraic difference between the SIGNAL at applied load and the SIGNAL at MINIMUM LOAD.

OUTPUT RESISTANCE – The resistance of the LOAD CELL circuit measured at the SIGNAL terminals with no load applied and with the excitation terminals open-circuited.

PRIMARY AXIS – The axis along which the LOAD CELL is designed to be loaded.

RATED OUTPUT or RO – The OUTPUT corresponding to CAPACITY, equal to the algebraic difference between the SIGNAL at (MINIMUM LOAD + CAPACITY) and the SIGNAL at MINIMUM LOAD.

RESOLUTION – The smallest change in load which produces a detectable change in the SIGNAL.

SHUNT CALIBRATION – Electrical simulation of OUTPUT by connection of shunt resistors of known values at appropriate points in the circuitry.

SIDE LOAD – Any load at the point of AXIAL LOAD application acting at 90° to the PRIMARY AXIS.

SIGNAL – The absolute level of the measurable quantity into which a force input is converted.

SPAN – Another name for RATED OUTPUT.

STATIC ERROR BAND or SEB – The band of maximum deviations of the ascending and descending calibration points from a best fit line through zero OUTPUT. It includes the effects of NONLINEARITY, HYSTERESIS, and non-return to MINIMUM LOAD. Normally expressed in units of %FS.

SEB OUTPUT – A computed value for OUTPUT at CAPACITY derived from a line best fit to the actual ascending and descending calibration points and through zero OUTPUT.

SYMMETRY ERROR – The algebraic difference between the RATED OUTPUT in tension and the average of the absolute values of RATED OUTPUT in tension and RATED OUTPUT in compression. Normally expressed in units of %RO.

TEMPERATURE EFFECT ON OUTPUT – The change in OUTPUT due to a change in AMBIENT TEMPERATURE. Normally expressed as the slope of a chord spanning the COMPENSATED TEMPERATURE RANGE and in units of %/°F or %/100°F.

TEMPERATURE EFFECT ON ZERO – The change in ZERO BALANCE due to a change in AMBIENT TEMPERATURE. Normally expressed as the slope of a chord spanning the COMPENSATED TEMPERATURE RANGE and in units of %RO/°F or %RO/100°F.

TEMPERATURE RANGE, COMPENSATED – The range of temperature over which the LOAD CELL is compensated to maintain OUTPUT and ZERO BALANCE within specified limits.

TEMPERATURE RANGE, OPERATING – The extremes of AMBIENT TEMPERATURE within which the LOAD CELL will operate without permanent adverse change to any of its performance characteristics.

TOGGLE – Another name for ZERO FLOAT.

ZERO BALANCE – The SIGNAL of the LOAD CELL in the NO LOAD condition.

ZERO DEAD BAND – Another name for ZERO FLOAT.

ZERO FLOAT – The shift in ZERO BALANCE resulting from a complete cycle of equal tension and compression loads. Normally expressed in units of %FS and usually characterized at FS = CAPACITY.

ZERO STABILITY – The degree to which ZERO BALANCE is maintained over a specified period of time with all environmental conditions, loading history, and other variables remaining constant.

A lot of applications require that only one axis of a force/torque sensor is used from 50% to 100% of the nominal load, while
the other axis of the sensor is used only up to 10% or even only up to 1% of the measuring range. Interface Inc. offers a
special “Matrix-Plus” calibration procedure to ensure optimum accuracy even in these application-specific working points.

The tasks of the calibration matrix are:
     a) Minimising the measurement error in the loaded measuring axis and
     b) Minimising the cross-talk in the remaining (unloaded) 5 axes.

Standard Calibration
In the case of low utilisation of some measuring axes, the error can have a relatively strong effect in these measurement
axes due to cross-talk, although it is significantly less than 1% based on 100% of the measuring range.

Advanced Calibration “Matrix-Plus”
Interface Inc. has developed a new calibration method, which optimises the display in the loaded measuring axis and
in the unloaded measuring axes. The characteristic field of the 6-axis sensor is represented by two matrices. Matrix A
describes the linear relationships, matrix B describes the non-linear relationships.

Matrix Plus with “Standard Constraints”
Special conditions are defined in the determination of the matrices so that the measurement errors are minimised even
at low forces and torques. Loads of 100%, 80%, 60%, 40% and 20% are mathematically optimised.

Matrix-Plus with “Simulated Operating Point”
It is even possible to take the application (operating point) into account while determining the matrices: this process
is called a “simulated operating point”. Thereby, accuracies of 1% to 0.2% of the actual value can usually be achieved.
In addition to the actual calibration load 100%, the application-specific load vector is also taken into account
mathematically.

Matrix Plus with “Calibration in the Operating Point”
Alternatively, a calibration is also possible at the operating point of the application. Customer-specific calibration uses
the actual loads and lever ratios of the customer-specific application. In one example, accuracies of 0.5% to 0.1% of
the actual value can be achieved. Suitable devices may have to be produced for the calibration in order to display the
special lever ratios of the application. This can result in additional costs and delivery times in individual cases.

Interface offers three primary Gold Standard software packages for the calibration of load cells or test machines.

1. Force Comparison ICS-202
2. Machine Calibration ICS-205
3. Dead-weight ICS-DW

All the software packages store calibration data for reference load cells, stepped load routines, ‘limits’ on performance criteria (where relevant) to help dramatically speed up the calibration process especially where repetitive routines are employed also at the same time helping to maintain accuracy and reduce errors.

System no.1 – Force Comparison (ICS-202)

This system requires dual channel data acquisition using either the Gold Standard PC Boards HRBSC/SCBxx or the dual channel 9840 model 9840-2xx-x. While both systems give you all the acquisition, display, manipulation, analysis and reporting functions the Gold Standard hardware has the additional option of adding a control board that provides total automation of the loading process. Regardless of how the applied force is controlled the software relies on measurements taken at stepped loading intervals, with those from a Calibration/Reference unit being compared to the Unit Under Test and then immediately performance figures are calculated and the error graph is plotted with comprehensive calculations of any parameter being available through the extremely flexible ‘Crystal’ report software. In-built formats are provided for a basis of ASTM-E74 and ISO-376 calibration reports. A concise operating manual will soon be available on this link.

System no. 2 – Machine Calibration (ICS-205)

While this system can be run using the dual channel hardware required by the above package it can also be operated using a single channel system more suited to the Field Calibration Engineer. This software takes the measurements from a Calibration/Reference load cell installed in the test machine and now compares the displayed reading of the test machine against the reference values at each stepped load interval and calculates the test machine errors at each step with tabulated results and graphical plots being offered plus immediate results can be made available in draft prior to confirmation and a signed copy. In-built formats are offered for ASTM-E4 and ISO-7500/1 calibrations. A concise operating manual will soon be available on this link.

System no.3 – Dead-weight (ICS-DW)

As above this package can be run with the dual channel hardware but only requires a single channel to measure the Unit Under Test while it is being loaded with known value reference dead-weights. Dead-weights are recognised as the most accurate way of applying known loads and the Gold Standard software will work with any number of weight-stacks to make the task of data collection a simple task of selecting the correct library files and clicking ‘Start’.  A concise operating manual will soon be available on this link.

A separate note will provide comparison details for the Gold Standard Hardware.

Although reference here has been made as ‘Force Calibration’ the software packages can also be used for Pressure or Torque calibrations with sensors that have strain-gauged bridge outputs or high-level signals of 4-20mA or +/-10V

Interface USA Colors

4-Wire

6-Wire

Interface UK Colours

6-Wire

NEW
European Colours

Interface offers a wide selection of indicators to cover many applications and here are the basic connection details for the 9840 which is one of the most popular units for calibration grade applications.

9840 Intelligent load cell indicator – 9-way D-type load cell connector

1. Excitation – High/Positive
2. Sense – High/Positive
3. Cell Output/Signal – High/Positive
4. Cell Output/Signal – Low/Negative
5. Sense – Low/Negative
6. Excitation – Low/Negative
7. Auto ID – A
8. Auto ID – B
9. Chassis Ground

Please contact us directly for details of the wiring for the other connectors.

Search with “What are the Interface load cell wiring colours?” for details of the most popular wiring/cable colour conventions.

The Interface DFI05L digital load cell indicator is optionally offered with the PCCx enclosure which provides a rugged casing for protection of indicator(s) and connecting wiring especially the mains voltage power supply leads. The rear panel provides an IEC style switched connector input and the load cell connection is via a standard D-type 15-way female connector (Male mating connector required for fitment to sensor). The wiring is as follows.

1. Positive Excitation
2. Positive Signal
3. Negative Signal
4. Negative Excitation
5. No connection
6. No connection
7. Logic input – Common #07
8. Logic input – CC.1 #08 {Tare}
9. Positive Excitation
10. Positive Sense
11. Negative Sense
12. Negative Excitation
13. No connection
14. Logic input – CC.2 #10 {Reset}
15. Logic input – CC.3 #09 {Peak/Valley}

NOTE.1: The DFI05L requires 6-way sense wiring so links should be fitted between pins 9-10 & 11-12 when wiring for 4-way.

NOTE.2: To enable the front panel buttons for TARE, RESET and PEAK/VALLEY a link should be fitted between Common (pin 7) and pins 9, 15 & 14 respectively.

This information is designed to cover both the Mk1 and Mk2 style devices.

All Interface load cells use eight full bridge strain gauges with each leg normally being rated at 350ohms.

The preferred excitation voltage for Interface load cells is 10VDC as this guarantees the closest match to the performance achieved by Interface during calibration.  The reason for this is that the gauge factor is affected by temperature.  Heat dissipation in the gauges is coupled to the flexure through a thin layer of epoxy glue; the gauges are kept at close to the ambient temperature of the flexure. However, the higher the power dissipation in the gauges, the larger the deviation between the temperature of the gauge and that of the flexure. For example, at 10VDC, a 350 ohm bridge dissipates 286m/w. A doubling of the voltage to 20VDC quadruples the dissipation to 1143m/w. This is a large amount of power to have in small gauges and can cause a substantial increase in the temperature gradient between gauges and flexure.  Conversely, dropping the voltage to 5VDC decreases the dissipation to 71m/w, not a significant drop from 286m/w.

The excitation voltage has an impact on sensitivity. For example, operating at 20VDC would decrease sensitivity by approximately 0.07% from the original Interface calibration, whereas operating the same load cell at 5VDC would increase sensitivity by less than 0.02%. This characteristic makes it possible to operate load cells at 5 or even 2.5VDC in order to save power.

Some, portable data loggers will automatically switch the excitation for short periods of time in order to conserve power. If the duty cycle is only 5% with 5VDC excitation, the heating effect is a tiny 3.6m/w. This could cause an increase in sensitivity of up to 0.023% from the original Interface calibration.

Variations in excitation voltage can cause small shifts in zero balance and creep. This effect is most noticeable when excitation voltage is first turned on. The solution for this effect is to allow the load cell to stabilize by operating it with 10VDC excitation for the time required for the gauge temperature to reach equilibrium, but this can take up to 30 minutes.

This chart details the mating connectors for the most common Interface force & torque sensor products.

Interface Mating Connectors

A peculiarity of the load cell industry is that all manufacturers seem to publicise figures for non-repeatability but these figures essentially have little or no merit. These figures could be thought of as reference values rather than actual determined values. The reasons for this are that there are no standards or definitions for a specific parameter. Although non-repeatability is generally thought to mean the variation in output for repeated loadings under identical loading and environmental conditions, there are no uniform procedures for conducting and reporting an appropriate test. There are also no means for excluding the non-repeatability of the test equipment which is often as significant as the non-repeatability of the load cell. Better measurements of the meaningful repeatability can be found in the following parameters:

• Eccentric load sensitivity
• Creep
• Interpolation error
• Temperature effect on output
• Temperature gradient sensitivity

Interface Low Profile load cells outperform all competitive products in these key parameters

When even greater repeatability is merited, a permanently installed stud  in the live end by Interface or by the user that is locked in under tensile load, provides still greater repeatability by isolating the load cell almost completely from end effects. The pre-loaded stud increases the height of an assembly, but the overall height is still the lowest of any load cell technology available. For ultimate repeatability special versions with integral machined studs offer further improvements over the jammed studs

AMTI model Gen5 6 channel amplifier.

Some AMTI sensors use commoned excitation to reduce the cable size to fit smaller body sizes and in some instances, a thinner cable helps with routing in more compact installations. The standard sensor design has 6 individual strain gauged Wheatstone bridges requiring a total of 24 cores and this can be reduced to 14 cores by commoning the excitation.

Wiring: The commoned excitation connections are made to the Fx bridge which has sufficient current to drive all 6 bridges.

Setup: It is important to set internally the excitation voltage for the remaining 5 bridges to the same value as Fx as the signal output for each bridge is calculated using the sensitivity and the excitation.

There are two connector options when connecting load cells to the BSC4 amplifier. Depending on which model was purchased all four channels may be incorporated in a single 37-pin D-sub connector, or 4x 5-pin M12x1 connectors – one for each channel.

The wiring for each is below:



The 9840 serial cable comprises normally 6-core screened cable even though only four cores are used and is fitted with a female 9-way D-type on one end and a female 15-way D-type on the other with wiring as follows.

Although today there is a proliferation of USB connections still numerous industrial applications rely on RS-232 for a dedicated port connection to a measuring device which in this case is the Interface 9840 calibration grade digital load cell indicator. Connecting the 9840 by either serial or USB allows the instrument to be controlled from the Gold Standard data acquisition software.

The most basic of the Interface load cell calibration certificates gives a single mV/V value but this figure has real value.

Many manufacturers only provide a Terminal value or in Interface terms RATED OUTPUT i.e. the measured signal value at full rated load, but the figure provided by Interface is the Static Error Band Output (SEB OUTPUT) which is a calculated best-fit value.

The SEB OUTPUT requires a minimum of 4 measurements at 3 points these being zero, 50% range ascending 100% range and 50% range descending.

For SSM & SM S-beam style units the provided value is that for tension measurements while the MB & MBI units are provided with compression values.

For more information contact us directly or via info@interface.uk.com

Understanding Force Calibration Standards: A Comprehensive Overview

When it comes to ensuring accuracy and reliability in force measurement, adherence to calibration standards is paramount. These standards provide guidelines and protocols for calibrating force-measuring instruments, ensuring their precision and traceability to internationally recognized reference standards. In this article, we’ll delve into some of the key force calibration standards, including NIST traceable, UKAS, ASTM E74, and ISO 376, highlighting their significance and differences.

Accreditation Body vs. Accreditation Standard

Accreditation Body

An accreditation body is an organization that assesses and certifies the competence of calibration laboratories to perform specific types of tests or measurements. Examples include UKAS in the UK and the American Association for Laboratory Accreditation (A2LA) in the U.S. These bodies ensure that accredited laboratories meet strict technical and quality management criteria.

Accreditation Standard

An accreditation standard, on the other hand, defines the requirements that a laboratory must meet to achieve accreditation. ISO/IEC 17025 is the most common accreditation standard for calibration laboratories worldwide. It specifies general requirements for the competence, impartiality, and consistent operation of laboratories, ensuring their results are reliable and globally accepted.

What Is ISO 17025?

ISO/IEC 17025 is the internationally recognized standard for testing and calibration laboratories. It outlines the necessary management and technical requirements for a laboratory to demonstrate its ability to produce valid results. Key elements include:

• Management Requirements: Focus on processes such as document control, risk management, and continuous improvement.
• Technical Requirements: Include personnel qualifications, method validation, equipment calibration, and measurement traceability.

Accreditation to ISO 17025 signifies that a laboratory is technically competent and operates a quality management system that meets rigorous global standards. This accreditation is critical for maintaining trust in calibration results across international borders.

Key Force Calibrations

Traceable Calibration 

A traceable calibration involves calibrating force measuring devices against reference standards directly traceable to an accredited body such as UKAS or NIST. This ensures that measurements are consistent and reliable, contributing to the credibility and quality of the calibration process.

NIST Traceable Calibration:

The National Institute of Standards and Technology (NIST) is a renowned authority in metrology, providing the foundation for measurement standards in the United States. NIST traceable calibration involves calibrating force measuring devices against reference standards directly traceable to NIST. This ensures that measurements are consistent and reliable, contributing to the credibility and quality of the calibration process.

All Interface load cells are calibrated to NIST traceable standards in Interface’s ISO1705 accredited lab before shipping, unless otherwise stated

UKAS Calibration:

The United Kingdom Accreditation Service (UKAS) is the national accreditation body for the United Kingdom, recognized globally for its rigorous assessment and accreditation of calibration laboratories. UKAS calibration entails calibration performed by laboratories accredited by UKAS (normally ISO17025), adhering to stringent quality management systems and technical competence criteria. Instruments calibrated by UKAS-accredited laboratories are deemed to meet internationally accepted standards of accuracy and reliability.

ASTM E74 Calibration:

ASTM International, formerly known as the American Society for Testing and Materials, develops and publishes technical standards for various industries, including force measurement. ASTM E74 is a standard specification for the calibration of force-measuring instruments, outlining procedures for calibration and verification of force-measuring devices. Compliance with ASTM E74 ensures that instruments meet specified accuracy requirements and adhere to standardized calibration procedures.

ISO 376 Calibration:

ISO 376 is an international standard that provides guidelines for the calibration of force-measuring instruments used in the testing and verification of materials and components. It defines calibration procedures, uncertainty estimation, and reporting requirements to ensure the accuracy and traceability of force measurements. ISO 376-compliant calibration ensures consistency and comparability of measurement results across different laboratories and testing environments.

Key Differences:

While these force calibration standards share the common goal of ensuring measurement accuracy and traceability, there are notable differences in their scope, application, and regional recognition. NIST traceable calibration is primarily recognized in the United States, while UKAS calibration holds significance in the United Kingdom and other countries recognizing UKAS accreditation. ASTM E74 is widely adopted in industries adhering to ASTM standards, particularly in North America, whereas ISO 376 enjoys global recognition, facilitating international harmonization of force calibration practices.

Force Calibration Standards and Interface Load Cells

All Interface load cells are factory-calibrated to one of the calibration standards discussed above. These calibrations are performed at our calibration facility, which is accredited to ISO/IEC 17025.

Calibration by Standard:

• Calibration Standard Devices: Load cells in the 1600 Gold Standard and 1800 Platinum Standard ranges are calibrated to ASTM E74 as a standard from as low as 2% of capacity. ISO 376 calibration is available upon request.
• General Load Cell Ranges: Models such as the 1000 Fatigue, 1100 Ultra Precision, and 1200 Precision ranges are supplied with individual NIST Traceable calibrations. ASTM E74 or ISO 376 calibrations can be provided on request.

For existing load cells requiring recalibration, we offer services tailored to your preferred standard. Please contact us to discuss your specific requirements.

Conclusion:

In conclusion, adherence to force calibration standards is essential for maintaining measurement accuracy, reliability, and traceability in force measurement applications. Whether it’s NIST traceable, UKAS, ASTM E74, or ISO 376 calibration, each standard plays a crucial role in ensuring the quality and consistency of force measurement results. By understanding the differences and significance of these standards, organizations can make informed decisions in selecting calibration services that meet their specific requirements and industry standards.

If you’d like further advice, please call us  on 01344 77666 or email us at info@interface.uk.com We’ll be happy to discuss your aims, look at all the options and costs so we can suggest the most suitable calibration to match your requirement.

Extraneous or off-axis loads can be due to many factors and one of these is ‘Eccentric Load’ Eccentric loads occur when the actual load path is parallel with the load axis but at a distance that creates a vector load path introducing a moment load that can affect the output signal level.

The radial design of the Interface Low Profile units has inherent resistance to off-axis loads and this is further enhanced by precision machining to balance the bridges while under load so errors are minimised when the loading is not perfectly aligned.

Interface guarantees the performance and specifies the maximum (worst case) errors under side force, moment loads and torsional effects.

For example the 1000 Series has a published specification (Note:1) for Eccentric Load Sensitivity of +/-0.1% per Inch, so even if you apply the load at an offset distance of 1.0” (25.4mm) you will see a worst case error of +/-0.1% or less. This means that you can have confidence in your loading system measurements under real-world working conditions not just in the laboratory conditions before you shipped it to the end-user.

Note:1 1000 Series datasheet ref: 1000FR v2.2 04-25-2018

In simple terms, overload happens when the force applied to a load cell surpasses its rated capacity. This can cause permanent deformation of the sensor, disrupting the precise processing needed for accurate data. The consequences of overloading are severe and can be catastrophic. Overloading can compromise the load cell’s structural integrity, leading to significant damage and potential system failure. This highlights the importance of understanding and managing overload conditions, and the value of having reliable overload protection in your load cells.

A zero offset greater than 20% clearly indicates overload. If the zero balance falls between 10% and 20%, it suggests a probable overload. It’s important to note that such mechanical damage is typically irreversible. While it might be possible to electrically re-zero the load cell, this does not restore the affected performance parameters, emphasizing the need for caution and proper handling.

Another potentially more dangerous type of overload is an impact load. Impact loads are sudden forces that can cause significant damage to load cells. If the live end of the cell moves more than 150% of its full capacity deflection relative to the dead end, the cell could be overloaded, regardless of the impact duration. The forces generated by impact loads can be extremely high, leading to potential overload and subsequent damage.

To learn more about load cell overload and how to prevent it, read our blog “Understanding and preventing load cell overload“.

1. Review Safe Overload Specifications

Begin by reviewing the specifications of each load cell to understand its capacity range. Interface provides the overload protection value in the product description, features, and specification datasheet. Refer to the mechanical specification of Safe Overload – %CAP for the specific values.

2. Use Interface Overload Protected Load Cells

Interface offers load cells with built-in overload protection. This feature restricts the movement of the center hub under load, preventing further deflection once a specific limit is reached. This is especially useful in applications where high impact or sudden loads are expected.

3. Regular Maintenance and Calibration

Conduct regular checks using tools like ohm meters to detect overload conditions early. Insulation resistance tests can also reveal potential issues indicating overload or other electrical problems.

TIP: Calibrate your load cells at least once a year to maintain accuracy and performance.

Overload detection and management are crucial for ensuring the reliable performance and longevity of load cells. By recognizing the signs of overload, managing impact loads, and taking preventive measures, users can preserve the integrity of their measurement systems. Regular maintenance and thoughtful design considerations are key to avoiding the negative effects of overload and ensuring accurate, long-term performance of load cells.

By following these guidelines, industries can ensure their load cells function accurately and reliably, maintaining the overall integrity of their testing and measurement systems.

To learn more about load cell overload and how to prevent it, read our blog “Understanding and preventing load cell overload“.