Force measurement: force gauges, torque testers and test stands

Force measurement includes tensile, compression, pulling, pushing and mechanical-resistance tests carried out on components, assemblies, materials and devices. In industrial settings, these checks make it possible to assess sample behaviour, compare different manufacturing processes and collect useful data for production, testing, maintenance and quality control.

The instrument normally used to measure force is the force gauge. The range includes analog and digital force gauges, models with integrated or external load cells, manual and motorised test stands, and complete systems developed for specific applications.

Torque testers are instead used for torsion tests, measuring the torque applied during tightening, loosening or rotation of a component. The section also includes cap torque testers, torque wrench test stands and structures dedicated to torsion testing.

How force is measured and which instrument to use

Force is measured with a force gauge, an instrument that detects tensile or compressive stress and converts it into a readable value. In digital models, measurement is carried out through a load cell, while analog force gauges use a mechanical system.

The SI unit of force is the newton, indicated by the symbol N. Depending on the model, the result can also be displayed in kilograms-force, pounds-force or other units available on the instrument.

A force gauge should not be selected solely according to the maximum value to be measured. The minimum expected force, type of test, load direction and required accuracy must also be considered.

To measure small forces or very low stresses, it is advisable to use a force gauge with a limited capacity and suitable resolution. A measuring range that is excessively wide compared with the actual test values may make small variations more difficult to assess.

Analog and digital force gauges

Analog force gauges are suitable for immediate checks where reading the value directly on the instrument scale is sufficient. They do not require a power supply and can be used for tensile and compression checks in production, maintenance and testing.

Digital force gauges offer more advanced functions, including instantaneous-value display, peak-value detection, internal memory and the setting of minimum and maximum limits for pass/fail checks.

When measurements requiring higher accuracy are needed, professional digital force gauges designed for more demanding checks can be used. These instruments can be operated manually or mounted on a test stand, according to the test and the level of operational repeatability required.

The ability to store and transfer results makes it possible to document inspections, compare series of samples and reduce errors associated with manual transcription.

Tensile and compression force measurement

Instruments used to measure tensile force are force gauges configured with hooks, grips or holding devices suitable for the sample. The test can be used to determine the force required to stretch, pull out, separate, remove or break a component.

Applications include checks on cables, wires, terminals, connections, packaging, springs, closures, bonded elements and mechanical assemblies. The peak value can be used to compare different materials, processes, batches or settings.

In compression tests, the force gauge instead measures the force required to compress, insert, crush, operate or deform a part. With suitable accessories, the same instrument can therefore be used as either a tensile force gauge or a compression force gauge.

Compression tests are used to check push buttons, switches, springs, seals, packaging, plastic components, mechanical devices and other parts subjected to a pushing force.

Force gauges with external load cells

When the sensor cannot be integrated into the instrument body or higher capacities are required, digital force gauges with an external load cell are used.

S-type load cells make it possible to measure both tension and compression. They can be installed in structures, test benches and configurations where the load must be applied along the axis of the cell.

R-type round load cells are intended for compression tests. MR versions have more compact dimensions and are particularly useful when installation space is limited.

Load-cell selection depends on the maximum expected force, direction of the applied stress, system geometry and the way the load is transmitted to the sensor.

Test stands for force gauges

Test stands make it possible to keep the force gauge and sample in a stable position, applying force along a controlled direction. Their use reduces operator influence and improves comparability between successive tests.

Manual test stands are available in vertical, horizontal or dual-position configurations. Movement can be controlled by a lever or handwheel, allowing the operator to apply tensile or compression force progressively.

More robust structures are suitable when higher loads or samples requiring greater stability must be managed. The choice between vertical and horizontal arrangement depends on part geometry, the accessories used and the type of test.

Motorised test stands apply movement at a controlled speed and are particularly suitable for repeated tests. Double-column versions offer greater rigidity and can be part geometry, the accessories used and the type of test.

Motorised test stands apply movement at a controlled speed and are particularly suitable for repeated tests. Double-column versions offer greater rigidity and can be used when high forces or larger test equipment are involved.

Automatic force and displacement tests

Digital force/displacement test stands make it possible to programme automatic sequences based on position or force.

In displacement-based cycles, it is possible to define the positions to be reached, the speed of the different stages, any dwell times and the number of repetitions. This mode is useful when the sample must be compressed, elongated, inserted or extracted over a predefined distance.

In force-based cycles, the test stand receives the values detected by the force gauge and manages movement according to the set thresholds. The test can be configured by defining load levels, operating speeds, the time during which each force must be maintained and the subsequent return stages.

The test stand display can show both displacement and the force transmitted by the force gauge.

Force gauge software makes it possible to acquire the force/time curve. By using the test stand software, the force detected by the force gauge is instead associated with the displacement measured by the structure, generating the force/displacement curve.

Dedicated systems for force testing

In addition to general-purpose force gauges and test stands, complete configurations developed for specific applications are also available.

The force gauge kit for Snook and Ciriello tests makes it possible to measure pulling and pushing forces during the manual handling of loads. The results collected can be used by the operator for subsequent evaluations. The kit can also be used to measure the force required to move trolleys and to check panic bars using the dedicated plate.

The sliding door kit makes it possible to measure the forces required during the opening, closing and movement of automatic doors, gates and other compatible sliding systems.

The crimp pull test stand measures the holding force of crimped cables, terminals and cable lugs. During the test, the sample is subjected to tension until pull-out, detachment, breakage or the condition required by the inspection is reached.

For the same application, a motorised horizontal digital test stand combined with the dedicated grip can also be used when a programmable test with controlled movement is preferred.

The digital belt tension tester makes it possible to check the tension of timing and auxiliary belts during installation and maintenance of engines, machinery and transmission systems.

Digital torque testers

Torque, or twisting moment, describes the rotational effect produced by a force applied at a certain distance from an axis. It is normally measured in newton metres.

Digital torque testers measure torque in both clockwise and counter-clockwise directions and can be used for tightening, loosening, rotation and torsional-resistance tests.

Torque testers with an integrated load cell are mainly intended for the inspection and in-house calibration of torque wrenches and torque screwdrivers. Their compact structure combines the sensor, display and controls in one body.

Torque testers with an external load cell instead separate the sensor from the display unit, making installation in test benches and dedicated configurations easier. The load cells are available in different measuring ranges, selected according to the expected torque.

For the inspection or in-house calibration of electric screwdrivers or impact tools, torque testers can be combined with joint simulators. These accessories act as damping elements and limit impulsive peaks transmitted to the load cell.

Portable digital torque testers are suitable for tests performed directly on components. Using Phillips, hexagonal, slotted or equivalent inserts, they make it possible to measure the tightening and loosening torque of screws, nuts, shafts, couplings, knobs and other rotating parts.

Cap torque testers

Cap torque testers are dedicated bench instruments used to measure the opening and closing torque of bottles, jars, vials and containers.

The sample is secured using adjustable supports while the operator manually rotates the cap. The instrument detects the applied torque and makes it possible to compare closures, containers, batches and capping-machine settings.

These checks are used in the food, cosmetics, pharmaceutical, chemical and packaging sectors, where it is important to verify the consistency of the closing process and cap behaviour during opening.

Software for force and torque data acquisition

Compatible digital force gauges and torque testers make it possible to transfer stored results to a PC and acquire measurements in real time.

During recording, it is possible to display the force/time or torque/time curve, export data and graph images, calculate average and peak values over the full acquisition or a selected section, and set start and stop conditions.

Graphical representation makes it possible to analyse not only the maximum value, but also the load trend during the test.

Torque wrench test stands and torsion test systems

Torque wrench test stands make it possible to carry out the inspection and in-house calibration of torque tools correctly. The structure supports the wrench and applies the load progressively through a handwheel-operated carriage.

When combined with a torque tester with an integrated or external load cell, they make it possible to compare the value set on the wrench with the torque actually measured, keeping the point of application more stable and reducing operator influence.

For torsion tests on components, a modular vertical test stand is available with a rotating lower base and a height-adjustable upper support. The system keeps the sample aligned and applies rotation manually and progressively, while the installed torque tester measures the generated torque.

How to choose a force gauge or torque tester

Selection should begin with the quantity to be checked: tensile force, compression force, tightening torque, loosening torque or belt tension.

The required measuring range, minimum expected force, direction of the applied stress, sample dimensions and gripping device needed to secure it correctly must then be assessed.

For direct and occasional checks, a portable force gauge may be sufficient. When greater stability, improved operational repeatability or frequent tests are required, a dedicated test stand or bench is preferable.

Applications requiring repeated cycles, controlled speeds, dwell times or force/displacement curves must be carried out with programmable digital test stands. To document the complete trend of the test, real-time software acquisition is instead required.

Calibration of force gauges and torque testers

Calibration makes it possible to verify instrument performance and keep results under control over time. Depending on the model and configuration, the force gauge or torque tester can be supplied with the corresponding calibration report.

Calibration concerns the instrument that measures force or torque. Test stands and benches instead perform the mechanical function of supporting the sample, guiding movement and applying the load under the conditions required by the test.