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Calibration Curve 101

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Calibration curves are essential for ensuring the accuracy of force measurements. They are used in a wide variety of test and measurement applications, including quality control, research, and engineering.

A calibration curve is a graph that shows the relationship between the output of a measuring instrument and the true value of the quantity being measured. In force measurement, a calibration curve is used to ensure that the force measuring device is performing accurately. In the context of load cell calibration, a calibration curve is a graphical representation of the relationship between the output signal of a load cell and the applied known loads or forces.

The load cell user will use a known force standard to create the calibration curve. The known force standard is applied to the force measuring device and the output of the instrument is logged via the supporting instrumentation. This process is repeated for a range of known forces.

The calibration curve for a load cell is created by plotting the output signals (typically in voltage or digital units) on the y-axis against the corresponding applied loads or forces on the x-axis. The resulting graph is the calibration curve.

Test and measurement professionals use the calibration curve to convert the load cell output to the true value of the force being measured. The curve helps to establish the relationship between the load and the output signal, and it provides a means to convert the load cell’s output into accurate force or weight measurements. For example, if the output is 100 units when a known force of 100 N is applied, then the calibration curve will show that the measurement using the load cell is accurate to within a certain tolerance.

Benefits of using a calibration curve in force measurement:

  • It ensures that the force measuring instrument is accurate and dependable.
  • It provides a way to convert the load cell output to the true value of the force being measured.
  • It can be used to identify and correct errors, including drift, sensitivity, overload and hysteresis.
  • It should be used for traceability and to track the performance of the measurement device over time.

Why does a calibration curve matter when calibrating load cells?

Load cells can be affected by a range of factors, including temperature variations, drift, and environmental conditions. The calibration curve helps identify and compensate for these factors. By periodically calibrating the load cell, any deviations from the original calibration curve can be detected, and appropriate corrections can be made to ensure accurate and reliable measurements.

The calibration curve for a load cell should be linear, indicating a consistent and predictable relationship between the applied load and the output signal. However, load cells may exhibit non-linear behavior, such as sensitivity variations or hysteresis, which can be accounted for and corrected through calibration.

The calibration curve allows for the determination of the load cell’s sensitivity, linearity, and any potential adjustments or corrections needed to improve its accuracy. It serves as a reference to convert the load cell’s output signal into meaningful and calibrated measurements when the load cell is used in practical applications for force or weight measurement.

Calibration curves are an essential tool for ensuring the accuracy of force measurements. They are used in a wide variety of applications, and they offer several benefits. If you engage in using load cells, it is important to understand the importance of calibration curves and how they can help you ensure accurate measurements.

Find all of Interface 101 posts here.

Interface recommends annual calibration on all measurement devices. If you need to request a service, please go to our Calibration and Repair Request Form.

ADDITIONAL RESOURCES

Interface Calibration 101

Interface Guides

Load Cell Sensitivity 101

Interface Force Measurement 101 Series Introduction

Extending Transducer Calibration Range by Extrapolation

Top Five Reasons Why Calibration Matters

Accurate Report on Calibration

System Level Calibration Validates Accuracy and Performance

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Interface strongly recommends when buying any force measurement sensor along with instrumentation that you request a system level calibration. The final step taken to confirm that a sensor and instrumentation are working properly together before leaving Interface is a system level calibration.

System level calibrations provide traceability and record for reference for validating performance and accuracy. It is important to review calibration certificates prior to use and for any troubleshooting. System level calibrations ensure that all system components, including connectors, cables, transducers, and instrumentation are ready to use out of the box.

Interface provides calibration to all individual force measurement components. A basic calibration for the load cell is performed and certified of how the transducer performs in isolation. Expert Interface Calibration Technicians always calibrate these devices to meet the design specification and the exact parameters outlined in the accompanying calibration certifications shipped with the part. A calibration certification characterizes the load cell performance across specific force range with different load points applied output from the load cell versus applied load, confirmed by the specification in voltage outputs, milliamps, or digital output types.

A system level calibration ensures that the performance of the transducer and instrumentation are operating as a system, together. A system level calibration and an associated certification proves the system pairing is functional and essentially plug-and-play ready.

The system level calibration is an important reference for traceability and troubleshooting for the entire system. It can help identify if a setting has been changed or if there is another issue that invalidated the system.

Interface can provide system level calibrations for load cells, torque transducers, multi-axis sensors and other measurement tools that are paired with indicators, amplifiers, USB, and digital instruments. Interface uses a very high quality NIST and NMI traceable mV/V transfer standard to ratiometrically scale or applied force to scale the system. We provide a separate digital indicator calibration certificate indicating how we scaled the instrument.

Interface guarantees our quality performance load cells, torque transducers, multi-axis sensors, and related instrumentation. We certify our products to meet or exceed the quality clauses outlined by the International Organization of Standardization (ISO).

Interface is A2LA Accredited for torque and force calibration in accordance with International Standard ISO/IEC 17025:2017.

From the time we designed our first load cells in 1968, we have been providing calibration solutions. We even calibrate other manufacturers load cells.  Every year, Interface performs more than 100,000 calibrations. Every transducer’s calibration data is stored at Interface, providing a permanent archive. We utilize NMI Certified Gold and Platinum Standard reference load cells and our Interface Gold Standard Calibration Software for all calibrations.

ADDITIONAL RESOURCES

Instrumentation Selection Guide

Top Five Reasons Why Calibration Matters

Recap of Accurate Report on Calibration

Regular Calibration Service Maintains Load Cell Accuracy

Shunt Calibration 101

Load Cell Basics Sensor Specifications

Top Five Reasons Why Calibration Matters

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Applied metrology is the measurement science developed in relation to manufacturing and other processes, ensuring the suitability of measurement instruments, their calibration, and quality control.

Calibration is the practice of evaluating and adjusting equipment to ensure precision and accuracy. Calibration for force measurement determines whether a sensor is working properly, as well if it needs repair or replacement.

Calibration is critical in the application of test and measurement because it provides controlled methods using equipment and systems that ensure reliability, accuracy, and quality.

We recently shared in our Accurate Report on Calibration seminar, the top five reasons why calibration matters. Below highlights each why.

#1 Reason Why Calibration Matters – Understanding Uncertainty

  • Measurement uncertainty is defined as an estimate of the range of measured values within which the true value lies or, alternatively, the degree of doubt about a measured value.
  • In every application, there will be an uncertainty requirement on the force measurement.
  • The equipment used to make the measurement must be traceable to a realization of the SI Newton unit of force within this required uncertainty.

#2 Reason Why Calibration Matters – Quality and Specifications

  • Calibration ensures the transducer is performing to listed specification.
  • It avoids costly impacts or escapes to manufactured goods and products.
  • Maintaining quality of manufactured device to original specifications is an important reason why calibration matters.
  • It certainly minimizes the cost of poor quality.

#3 Reason Why Calibration Matters – Minimize Downtime

  • Proactive maintenance will always take less time than reactive problem solving and repairs.
  • Identify and repair or replace system components before they fail through regular calibration.
  • Plan calibration intervals to minimize downtime, as a schedule is preventative maintenance.

#4 Reason Why Calibration Matters – Data Accuracy

  • All load cells are subject to potential performance degradation due to mistreatment or drift, impacting data integrity.
  • Pre and post test verification provide assurances in data validity.
  • Confidence in critical measurements is imperative.

#5 Reason Why Calibration Matters – Accreditation and Certifications

  • Calibrations provide adherence to quality management systems and requirements, especially ISO certifications and compliance.
  • It assures that measurements gathered within the valid calibration period are reliable, trustworthy, and defensible.
  • Traceability of measurement is guaranteed with certifications.

To start, every sensor Interface manufactures is calibrated and certified in our fully accredited calibration labs before it leaves our facilities. We do so under ISO 17025 standards with full NIST traceability for quality assurance. Annually, we provide more than 100,000 calibrations on force and torque measurement devices.

We also provide complete calibration services and repair on any sensor we make, as well as other manufacturer’s equipment. Our experienced calibration lab technicians offer a complete range of calibration services for load cells, torque transducers and other force measurement devices, including:

  • Scheduled Repairs for Ongoing Inventory Management
  • RMA Tracking and Permanent Archive of Test Data
  • Custom Calibration Services
  • Certification

Calibration is a necessity as any product can degrade, resulting in a decline in accuracy. Interface recommends every device go through a calibration service annually to maintain the integrity of the sensor performance. If you need assistance in scheduling a calibration service or requesting help, contact us here.

We also offer a range of calibration grade equipment for labs and to use for self-service calibration.  This includes our verification load frames, calibration systems, calibration grade load cells and lab instrumentation. Read Calibration Grade Load Cells and Systems and Additional Interface Calibration Grade Solutions to learn about these and other products.

ADDITIONAL RESOURCES

Recap of Accurate Report on Calibration

Interface Calibration 101

GS-SYS04 Gold Standard® Portable E4 Machine Calibration System

Shunt Calibration 101

Extending the Calibration Range of a Transducer

Calibration-and-Repair-Brochure-1