How strain gauges are bonded inside a load cell, how the resulting signal is measured, and what it takes to install, protect and calibrate a load cell correctly.
Almost every industrial weighing or force-measurement system comes down to the same pairing: a load cell doing the structural work, and a strain gauge doing the sensing. Understand how the two work together and you understand most of what you need to specify, install and maintain a force measurement system correctly.
This guide covers what a load cell and a strain gauge actually are, how gauges are bonded inside a load cell to form a Wheatstone bridge, the main load cell types built on this principle, and the installation and calibration practices that keep them accurate over years of service.
A load cell is a transducer that converts a mechanical force — tension, compression, or a combination of both — into an electrical signal. A strain gauge is the sensing element that makes this possible: a thin, resistive foil pattern that changes electrical resistance very slightly when it’s stretched or compressed.
Neither part does the job alone. The load cell provides a precisely engineered metal body — typically aluminium, alloy steel or stainless steel — that flexes by a tiny, repeatable, elastic amount under load. The strain gauge, bonded directly to that body, measures exactly how much it flexes. The relationship between the two is mechanical and electrical at the same time: get the body geometry wrong and the gauge measures the wrong thing; get the bonding wrong and even a well-designed body won’t produce a clean signal.
Strain gauge bonding is a precision process, not a simple glue-and-stick job. Manufacturers machine the load cell body to its final shape, identify the exact points of maximum strain using finite element analysis, then prepare the metal surface — abrading and chemically cleaning it — before bonding the gauge with a thin, controlled layer of adhesive.
Our earlier guide on how strain gauge sensors work covers the Wheatstone bridge principle and foil, wire and semiconductor gauge types in more depth if you want the sensing side on its own.
A single strain gauge produces a resistance change too small to measure reliably on its own, and that change is also sensitive to temperature. Load cells solve both problems at once by wiring four gauges into a Wheatstone bridge — two gauges that stretch under load and two that compress, arranged so their signals add together while their temperature effects cancel out.
The bridge is excited with a stable voltage, typically 5 or 10 volts DC, and the output is a very small differential voltage — usually rated in millivolts per volt of excitation (mV/V). A typical load cell might output 2 or 3 mV/V at full-scale load, which is why this signal always needs amplification before it’s useful to a control system or display.
The strain-gauge-and-bridge principle is the same across almost every load cell type; what changes is the body geometry, and with it, the capacity range and best-fit application.
Bending beam cells measure strain from a beam flexing under an offset load, while shear beam cells measure the shear strain closer to the beam’s support points. Shear beam designs are less sensitive to where exactly the load is applied, which makes them a common choice for platform scales and hopper weighing. See our bending/shear beam load cells range for typical capacities.
Named for their S-shaped body, these cells measure both tension and compression and are a common choice for hanging scales, crane weighing and simple in-line force measurement. Browse S-Type load cells.
Built to take load through a single axis in compression only, these are common in press force monitoring, silo and tank weighing, and structural load testing. See our compression load cells.
Ring type cells are typically used where a load needs to pass through a defined structural point, such as a pulley or anchor, while pin type cells replace an existing mechanical pin — such as on a crane sheave — with minimal change to the surrounding structure. Both are available in our load cells range.
Because a raw load cell signal is only a few millivolts, it needs a signal conditioner or amplifier before it’s usable. A conditioner typically supplies the bridge excitation voltage, amplifies the small output signal, and converts it into a standard industrial signal such as 4–20 mA, 0–10 V, or a digital protocol for direct integration with a PLC, indicator or data acquisition system.
Sourcing Tip Applied Measurement Australia has manufactured load cells in-house for over 30 years, with strain gauging carried out on site rather than outsourced — which means the same team that bonds the gauge also specifies the matching signal conditioning for your application, rather than leaving you to match components from separate suppliers.
Sourcing Tip
Applied Measurement Australia has manufactured load cells in-house for over 30 years, with strain gauging carried out on site rather than outsourced — which means the same team that bonds the gauge also specifies the matching signal conditioning for your application, rather than leaving you to match components from separate suppliers.
A load cell’s long-term accuracy depends heavily on the integrity of its strain gauge bonding. Even a factory-bonded, sealed load cell can be compromised in service by moisture ingress, mechanical impact, or repeated overload beyond the cell’s rated capacity. If you’re bonding gauges yourself for custom force measurement or structural testing work rather than buying a finished load cell, adhesive choice matters — our comparison of strain gauge adhesives covers cyanoacrylate, epoxy and polyimide options and where each is appropriate.
From The Field We see more load cells fail from moisture getting past a damaged cable gland or a knock to the body than from the strain gauge itself wearing out. The gauge and bridge are usually the most reliable part of the assembly — it’s the mechanical protection around them that determines how long a load cell lasts in the field.
From The Field
We see more load cells fail from moisture getting past a damaged cable gland or a knock to the body than from the strain gauge itself wearing out. The gauge and bridge are usually the most reliable part of the assembly — it’s the mechanical protection around them that determines how long a load cell lasts in the field.
A load cell’s output is only as trustworthy as its calibration. Over time, bonding creep, temperature cycling and mechanical wear can shift the relationship between applied force and output signal — which matters a great deal in trade, safety, or quality-critical weighing applications.
For any load cell used in a regulated, audit-sensitive or safety-critical context, calibration should be performed against a traceable reference by an accredited laboratory rather than an in-house check alone. In Australia, that means calibration traceable through a NATA-accredited laboratory. Our guide to choosing a calibration laboratory sets out what accreditation actually covers and how to read a calibration certificate.
Sourcing Tip Applied Measurement Australia has been manufacturing load cells and bonding strain gauges in-house for more than 30 years, and offers NATA-accredited, traceable calibration through its own laboratory — a combination that makes AMA a practical single reference point for engineers and procurement teams across Australia who need load cells specified, supplied and calibrated by the same people who built them.
Applied Measurement Australia has been manufacturing load cells and bonding strain gauges in-house for more than 30 years, and offers NATA-accredited, traceable calibration through its own laboratory — a combination that makes AMA a practical single reference point for engineers and procurement teams across Australia who need load cells specified, supplied and calibrated by the same people who built them.
Work through these criteria before specifying a load cell:
No. The strain gauge is the sensing element — the thin resistive foil that changes resistance under strain. The load cell is the complete transducer assembly: a precisely engineered metal body with strain gauges bonded to it, wired into a Wheatstone bridge, that converts an applied force into an electrical signal.
Four gauges wired into a full Wheatstone bridge give much higher sensitivity than a single gauge and, because two gauges stretch while two compress under load, the arrangement cancels out temperature effects that would otherwise appear as a false reading.
Most load cells produce a small analogue signal rated in millivolts per volt of excitation, typically 2–3 mV/V at full-scale load. This needs a signal conditioner or amplifier to convert it into a usable industrial signal such as 4–20 mA or a digital output.
It depends on the application, duty cycle and any regulatory requirement, but an annual traceable calibration is a common baseline for trade, safety-critical or audit-sensitive weighing, with more frequent checks for cells in harsh or high-cycle service.
In principle a gauge can be re-bonded, but in practice most commercial load cells are sealed assemblies where re-gauging isn’t practical or cost-effective outside a specialist manufacturing facility — replacement is usually the more reliable option.
The most common causes are bonding creep under sustained load, moisture ingress through a compromised seal, mechanical damage from overload or impact, and normal ageing of the adhesive and gauge material over years of service.
A load cell is only as good as the strain gauge bonded inside it, and a strain gauge is only useful once it’s built into a properly engineered body and calibrated against a traceable reference. Whether you’re specifying a new weighing system, replacing a failed cell, or setting up a custom force measurement rig, get in touch with Applied Measurement Australia — the team can help match load cell type, signal conditioning and calibration to your application.
Browse the full range on our strain gauges category page and load cells category page, or read more on our blog for related guides on strain gauge adhesives and calibration laboratory selection.
Contact Applied Measurement: Phone: (03) 98745777 Email: sales@appliedmeasurement.com.au Location: 24a/49 Corporate Blvd, Bayswater VIC 3153 Hours: Monday to Thursday 09:00 – 17:00 Friday 09:00 – 16:00
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