Basics about Strain Gauges

Technical Terms

Gauge Length

This dimension represents the actual grid length in the sensitive direction.

Gauge Resistance 

The gauge resistance is the electrical resistance of an unbonded gauge at room temperature and subject to no external stress. 

Gauge Factor

The amount shown in the following equation is called the gauge factor. In this equation, ε indicates the strain generated due to uniaxial stress in the direction of the strain gauge axis. ΔR/R shows the ratio of resistance change due to strain ε.


Transverse Sensitivity

The gauge also exhibits sensitivity in the direction perpendicular to the axial direction. The amount shown in the following equation due to the uniaxial strain (εt) in the direction perpendicular to the gauge axis, and the resistance variation generated thereby, is called transverse sensitivity (Kt).


Temperature Compensation Range

The temperature range within which thermal output meets a specification with a self temperature compensated gauge.

Self Temperature Compensated Gauge

A strain gauge made so that thermal output is as little as possible when adhered to a material to be measured with a particular coefficient of thermal expansion within a specified temperature range. We term self temperature compensated gauges of within ±1.8 × 10−6 strain per 1℃ capability a self temperature compensated gauge.

Operating Temperature Range

This range is the temperature range within which a strain gauge can be used continuously under appropriate conditions.

Strain Limit

The strain limit is the maximum amount of strain under which a strain gauge can operate under a given condition without suffering damage.

Fatigue Limit

The number of times a certain amount of strain is applied mechanically to an adhered strain gauge until change of 100×10−6 strain with regard to an initially indicated strain is observed.

Strain gauge shapes

Strain gauges are available in shapes suitable for any application.
Select a gauge shape that meets measuring goals.

Number of elements 1 element 2 elements 2 elements
Name Single-element Cross Cross
Arrangement Stacked Plane
Number of elements 3 elements 3 elements 5 elements
Name  Rosette Rosette 5-element
Arrangement Stacked Plane

Selecting a gauge length

Measurement object

As required by the object being measured, a short-length gauge may be used for localized strain measurement, and a long-length strain gauge for averaged strain measurement.
Averaged: For nonhomogenous materials, an adequate length of material that allows strain to be averaged is required. To measure nonhomogenous material such as concrete consisting of cement and aggregate, a gauge with a length about 3 times that of the aggregate grain size is used.

Gauge length Measurement object
0.2 to 1mm Stress concentration measurement
2 to 6mm General strain measurement in metal
10 to 20mm General measurement of mortar, wood, FRP, etc.
30 to 120mm General measurement of concrete


The response of a strain gauge depends on the gauge length and the elastic wave (longitudinal wave) of the material being measured.

Gauge length (mm) 0.2 1 3 5 10 30 60
Steel 660 530 360 270 170
Concrete 120 50 20


Gauge width

A narrower-type gauge (FLK type) with the same gauge length is also available. Select a strain gauge with a narrow gauge width for narrow specimens such as pipes and round sticks.

FLA Type
FLK Type


Name of each part of strain gauge

Pictures of each strain gauge given for the strain gauge series are shown enlarged so they are easier to see. Note that they are not shown actual size.