BF120-3AA Precision Strain Gauges (120Ω)
High-precision foil strain gauges for load cell applications with 120Ω resistance
Introduction
The BF120-3AA strain gauge is a precision sensor designed for load cell applications. These foil-type strain gauges feature a 120Ω nominal resistance and are constructed with advanced materials for excellent stability, linearity, and temperature compensation.
Key Features
High Precision
±0.1% linearity
Optimal Resistance
120Ω nominal resistance
Temperature Compensated
For various materials (steel, aluminum, etc.)
Foil Technology
Etched metal foil sensing element
Robust Construction
Fiberglass-reinforced epoxy backing
Long-term Stability
Excellent creep and hysteresis performance
Technical Specifications
| Resistance | 120Ω ±0.3% |
|---|---|
| Gauge Factor | 2.0 ±0.5% |
| Gauge Length | 3mm |
| Strain Limit | ±1.5% (15,000με) |
| Linearity | ±0.1% |
| Temperature Range | -30°C to +80°C |
| Thermal Output | ±0.5με/°C (on steel) |
| Excitation Voltage | Max 10V DC/AC |
| Grid Material | Constantan alloy |
| Backing Material | Fiberglass-reinforced epoxy |
| Dimensions | 6.4mm × 3.3mm × 0.08mm |
Wiring Configuration
| Connection | Description | Wheatstone Bridge Position |
|---|---|---|
| Red Wire | Positive excitation (+V) | Bridge input |
| Black Wire | Negative excitation (-V) | Bridge input |
| Green Wire | Positive signal (+S) | Bridge output |
| White Wire | Negative signal (-S) | Bridge output |
Installation Guide
- Surface Preparation: Clean mounting surface with solvent and lightly abrade
- Alignment: Position gauge carefully along strain axis
- Bonding: Apply thin layer of specialized strain gauge adhesive
- Curing: Follow adhesive manufacturer’s curing instructions
- Wiring: Solder lead wires using minimal heat
- Protection: Apply protective coating against moisture
Wheatstone Bridge Configuration
Full Bridge Configuration
For maximum sensitivity, use four active gauges:
- Two gauges in tension (R1, R3)
- Two gauges in compression (R2, R4)
- Output voltage Vout = (Vin × GF × ε)/4
Where GF is gauge factor and ε is strain
Signal Conditioning
Instrumentation Amplifier
Recommended gain: 100-1000×
Input impedance >10MΩ
CMRR >90dB
Excitation Voltage
Typical: 5V DC
Maximum: 10V DC
Stabilized power source required
Filtering
Low-pass filter: 10-100Hz cutoff
50/60Hz notch filter recommended
Troubleshooting
Zero Drift
- Check for temperature variations
- Verify proper curing of adhesive
- Ensure stable excitation voltage
Noisy Signal
- Check for loose connections
- Verify proper shielding
- Add appropriate filtering
Incorrect Output
- Verify gauge orientation
- Check bridge configuration
- Test individual gauge resistance
Application Examples
Load Cells
Precision force measurement
Structural Testing
Stress analysis on beams
Industrial Weighing
Process control systems
Automotive Testing
Component fatigue analysis
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