BX120-3AA High Precision Resistance Strain Gauge

BX120-3AA High Precision Resistance Strain Gauge is a high-precision metal foil resistive strain gauge designed for experimental stress measurement, structural load monitoring, and transducer prototyping. Manufactured with an ultra-thin etched Constantan foil grid bonded to a polyimide backing film, this gauge exhibits a nominal resistance of exactly 120 Ohms, making it fully compatible with classical bridge completion circuits, Wheatstone bridge boxes, and laboratory strain indicator instruments. Specifically, mechanical elongation or compression of the underlying structural material changes the electrical resistance of the grid with a calibrated Gauge Factor of 2.08. Furthermore, its miniature carrier footprint allows installation onto tightly radiused surfaces, miniature mechanical linkages, and compact load cell bodies.

Key Features:

• Standard 120Ω Nominal Resistance: Globally recognized standard impedance compatible with all commercial strain indicator bridges.
• High-Stability Constantan Foil Grid: Etched copper-nickel alloy provides exceptional linear response and minimal thermal drift.
• Flexible Polyimide Film Carrier: Conforms easily to curved pipes, shafts, and irregular mechanical surfaces.
• High Strain Measurement Limit: Measures extensive mechanical strains up to 20,000 µε (2.0% elongation).
• Integrated Solder Tabs: Pre-tinned connection pads facilitate secure soldering of miniature lead wires.

Technical Specifications:

• Nominal Resistance: 120.0Ω ± 0.5Ω
• Gauge Factor (Sensitivity): 2.08 ± 1%
• Strain Limit: 20,000 µε
• Operating Temperature Range: -30°C to +80°C
• Temperature Compensation: Matched to mild steel (thermal expansion coefficient ≈ 11 × 10^-6 / °C)
• Insulation Resistance: > 10,000 MΩ (at 100V DC)
• Grid Dimensions: 3.0mm × 2.0mm

Mechanical Specifications:

• Grid Material: Etched Constantan Metal Alloy (3-5µm foil thickness)
• Backing Material: Modified Polyimide Carrier Film (30µm thickness)
• Carrier Dimensions: 6.6mm × 3.6mm
• Installation Adhesive: Cyanoacrylate (super glue) or two-part epoxy adhesive

Dimensions:

• Total Length: 6.6mm
• Total Width: 3.6mm
• Thickness: ≈ 0.035mm (35µm)
• Gauge Weight: ≈ 0.02g

Pinout and Wiring:

• Pad 1: Solder thin insulated copper lead wire to one side of Wheatstone bridge arm.
• Pad 2: Solder lead wire to opposite bridge node.

Datasheet Reference:

• Review strain gauge installation procedures and bridge circuit mathematics in the Texas Instruments Strain Gauge Measurement Guide PDF.

Commonly Used in:

• Structural Load Testing: Quantifying micro-strain across steel beams, building columns, and pressure vessel walls.
• Automotive Chassis Dynamometry: Mapping torsional shear and bending stresses during suspension fatigue testing.
• Educational Physics Laboratories: Demonstrating Hooke’s law, Young’s modulus, and Poisson’s ratio in materials testing fixtures.

Applications:

• Structural Beam Deflection: Bonding onto I-beams and concrete reinforcement rebar to detect structural settlement in buildings.
• Shaft Torsion Measurement: Attaching at 45-degree angles to rotating axles to measure mechanical horsepower and torque.
• Custom Load Cell Building: Constructing 4-gauge full bridge load cells inside miniature robotic gripper fingers.

Equivalent Models:

• BF350-3AA 350-Ohm Strain Gauge: Higher-resistance foil gauge reducing internal excitation heating during continuous testing runs.
• Kyowa KFG-3-120-C1: High-precision Japanese constantan foil strain gauge calibrated for 120-ohm bridge conditioning electronics.
• Tokyo Measuring Instruments FLA-3-11: General-purpose 120-ohm foil strain gauge designed for mild steel and aluminum alloy substrates.

Package Includes:

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