The BX120-3AA High Precision Resistance Strain Gauge is a precision foil strain sensor designed for measuring mechanical strain and deformation in structural testing, industrial equipment, research, load-cell development, and force measurement applications. BDTronics offers this 120Ω strain gauge for engineers, researchers, students, and sensor manufacturers requiring a compact resistance-based strain measurement element.

The gauge uses a Constantan foil grid mounted on a flexible carrier film. When bonded to a suitable surface, mechanical deformation changes the resistance of the foil grid. This small resistance change can be measured using a Wheatstone bridge circuit and an instrumentation amplifier or dedicated load-cell ADC such as an HX711.

Features:

• 120Ω nominal resistance for precision strain measurement

• BX120-3AA configuration with approximately 3mm gauge length

• Constantan foil sensing grid

• Typical gauge factor of approximately 2.0

• High resistance accuracy with ±0.1% nominal resistance tolerance

• Designed for accurate measurement of mechanical strain and deformation

• Flexible carrier film for mounting on suitable test surfaces

• Low hysteresis for repeatable measurements during cyclic loading

• Temperature-compensation characteristics for improved measurement stability

• Compact size for laboratory and sensor-development applications

• Suitable for Wheatstone bridge strain measurement circuits

• Can be used in load-cell, force-sensor, torque-sensor, and structural monitoring designs

Specifications:

Working Principle:

A strain gauge converts mechanical deformation into a measurable change in electrical resistance.

When the BX120-3AA is properly bonded to a surface, stretching or compressing that surface causes the Constantan foil grid to deform. The resistance of the grid changes proportionally to the applied strain.

Because the resistance change is very small, strain gauges are commonly connected as part of a Wheatstone bridge. The resulting bridge voltage can then be amplified and converted into a digital measurement using an instrumentation amplifier, ADC, or strain-gauge interface such as the HX711.

For a basic quarter-bridge setup, the BX120-3AA can be used as the active strain element while precision resistors form the remaining bridge arms. Half-bridge and full-bridge configurations can also be used when multiple strain gauges are installed.

Wheatstone Bridge and Measurement:

The gauge itself is a passive resistance element and does not directly provide a digital output. A suitable measurement circuit is required.

A typical strain measurement system consists of:

BX120-3AA strain gauge → Wheatstone bridge → instrumentation amplifier / ADC → microcontroller

For Arduino, ESP32, STM32, Raspberry Pi-based measurement systems, or custom instrumentation, an appropriate low-noise strain-gauge amplifier and ADC should be used.

The 2–10V recommended excitation range should be considered when designing the bridge circuit. Actual excitation voltage should also account for gauge heating, bridge configuration, measurement accuracy, and the manufacturer's applicable limits.

Installation:

Proper installation is essential because the strain gauge measures deformation through the surface to which it is bonded.

1. Prepare a clean, smooth measurement surface.

2. Remove contaminants such as oil, grease, dust, oxidation, and loose material.

3. Position the BX120-3AA accurately along the intended strain direction.

4. Use an adhesive appropriate for the substrate and measurement environment.

5. Ensure the gauge is firmly bonded without air bubbles or loose areas.

6. Carefully attach measurement wires to the gauge terminals.

7. Protect the gauge from moisture, mechanical damage, and excessive environmental contamination where necessary.

8. Allow the bonding process to complete before applying mechanical load.

9. Calibrate the complete Wheatstone bridge and measurement system before taking quantitative measurements.

Applications:

• Load cell development

• Force sensor manufacturing

• Torque sensor development

• Pressure and force measurement systems

• Structural load testing

• Beam and cantilever strain measurement

• Mechanical stress analysis

• Material testing

• Industrial equipment monitoring

• Machine component stress measurement

• Laboratory research

• Engineering experiments

• Robotics force sensing

• Custom weighing systems

• DIY load-cell projects

• HX711-based strain measurement

• Arduino strain measurement

• ESP32 strain measurement

• Precision instrumentation

Mechanical Specifications:

• Substrate: Flexible carrier film

• Grid: Constantan foil

• Protective Layer: Light protective coating

• Gauge Length: Approximately 3mm

• Gauge Width: Approximately 2mm

• Backing Size: Approximately 7 × 5mm

• Thickness: Approximately 0.02mm excluding lead tabs

• Lead Tabs: Suitable for connecting measurement wires

Wiring:

The BX120-3AA has two electrical connection points associated with the resistance element. The gauge is normally incorporated into a Wheatstone bridge rather than connected directly to a standard digital input.

Use short, low-resistance measurement connections where practical. Shielded wiring can help reduce electrical noise in precision measurement systems, particularly when the strain gauge is located far from the amplifier or ADC.

The exact bridge wiring depends on whether the gauge is being used in a quarter-bridge, half-bridge, or full-bridge configuration.

Temperature and Measurement Stability:

Temperature changes can affect strain-gauge resistance independently of mechanical strain. The supplied specification describes the BX120-3AA as having temperature-compensation characteristics, but the overall measurement system can still experience thermal effects from the gauge, substrate, adhesive, wiring, and bridge resistors.

For high-accuracy measurements, temperature compensation and calibration should be considered as part of the complete sensor design.

Important Notes:

The BX120-3AA is a bare strain-gauge sensing element, not a complete load cell or digital weight sensor. It requires suitable bonding, Wheatstone bridge circuitry, signal amplification, and calibration to produce useful strain or force measurements.

The actual relationship between measured strain and force depends on the mechanical structure, material properties, gauge placement, bonding quality, bridge configuration, and calibration procedure.

Package Includes:

• 1 × BX120-3AA High Precision Resistance Strain Gauge 120Ω

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