Strain Gauge Resistance Variation Calculation (with Example)

Calculate Strain Gauge Resistance Change: Example Calculation

This guide explains how to calculate the resistance change of a strain gauge under load. We'll break down the concept of gauge factor and strain before walking through a practical example.

What is a Strain Gauge Carrier?

In strain gauge applications, the 'carrier' refers to the physical object or structure where the strain gauge is mounted. When the carrier undergoes stress or deformation, it transfers the strain to the attached strain gauge, causing a change in the gauge's resistance.

Understanding Gauge Factor

The gauge factor (GF) is a crucial parameter that quantifies the sensitivity of a strain gauge to strain. It's defined as the ratio of the fractional change in electrical resistance to the mechanical strain.

Formula:

• GF = (ΔR/R) / ε

Where:

• GF = Gauge factor
• ΔR = Change in resistance
• R = Resistance under no load
• ε = Strain

Example Calculation

Let's calculate the resistance variation for a strain gauge with the following characteristics:

• Strain Gauge Grid Length: 1cm (This information is not directly used in the calculation but provides context about the gauge's physical size)
• Grid Lines: 10 (This information is also not directly used in the calculation)
• Gauge Factor (GF): 2
• Resistance Under No Load (R): 120Ω
• Strain (ε): 50 × 10−6

1. Calculate the Change in Resistance (ΔR):

We rearrange the gauge factor formula to solve for ΔR:

• ΔR = GF * R * ε
• ΔR = 2 * 120Ω * 50 × 10−6
• ΔR = 0.012Ω

Therefore, the resistance of the strain gauge will change by 0.012Ω when subjected to a strain of 50 × 10−6.

Key Takeaways:

• Strain gauges are valuable tools for measuring strain, which is the deformation of a material under stress.
• The gauge factor is a critical parameter that determines the sensitivity of the strain gauge.
• By understanding the relationship between gauge factor, strain, and resistance change, we can accurately measure strain in various applications.