What it is

The KFGS is Kyowa's general-purpose foil strain gage, supplied here with gage leads only — silver-covered copper wires 25 mm (0.98 in) long — for installations where the wiring is soldered on site. It uses a polyimide resin base approximately 14 µm (0.00055 in) thick and offers superior flexibility, with excellent humidity resistance for measuring indoors and in the field, and is available in a variety of gage lengths and patterns for use in a wide range of applications.

• Gage factor approximately 2.1
• Gage resistance 60 Ω, 120 Ω, 350 Ω, 500 Ω, or 1000 Ω
• Gage lengths from 0.2 mm (0.008 in) to 30 mm (1.181 in)
• Uniaxial base sizes from 3.9 × 1.4 mm (0.154 × 0.055 in) to 37 × 5.2 mm (1.457 × 0.205 in)
• Uniaxial, biaxial, triaxial, quadriaxial, and five-element patterns
• Operating temperature −196 to 150 °C (−321 to 302 °F) depending on adhesive
• Self-temperature-compensation range 10 to 100 °C (50 to 212 °F)
• Strain limit approximately 5.0%, fatigue life 1.2 × 10⁷ cycles at ±1500 µm/m
• RoHS compliant

What it measures

• General stress measurement on metal under a general environment
• Surface strain on concrete and mortar with small aggregate
• General stress measurement on wood and lumber
• Residual stress by the cutting method — T-F7 gage-terminal patterns
• Residual stress by the boring method — D28 triaxial plane pattern
• Concentrated stress and stress distribution at 8 to 12 mm intervals — D9, D19, and D39 five-element patterns
• Torque — D2 and D31 biaxial plane patterns, or C15 and C16 shear patterns used in combination
• Poisson's ratio and stress analysis — D16 biaxial and D17 triaxial stacked rosettes
• Sensing elements for transducers — high-resistance 350 Ω, 500 Ω, and 1000 Ω uniaxial C1 patterns

Base, compensation, and endurance

Polyimide base, 14 µm. The polyimide resin base is approximately 14 µm (0.00055 in) thick and offers superior flexibility, with excellent humidity resistance for use when measuring indoors and in the field.

Self-temperature compensation matched to the substrate. Each gage carries a linear expansion coefficient code selected to match the test material — 11 for common steel (11.7), 16 for SUS304 stainless steel (16.2), 23 for A2014-T4 aluminum alloy (23.4), 27 for magnesium alloy (27.0), and 5 for lumber on selected uniaxial patterns. Self-temperature compensation covers 10 to 100 °C (50 to 212 °F), and the base color identifies the applicable linear expansion coefficient.

Strain limit and fatigue life. The strain limit is approximately 5.0% at normal temperature, with a fatigue life of 1.2 × 10⁷ cycles at a ±1500 µm/m strain level. The strain limit is the mechanical strain at which the strain reading differs from mechanical strain by more than ±10% under a simple tension load, or at which the gage becomes disconnected or detached.

Operating temperature and adhesive

The adhesive sets the operating temperature of the installation and is ordered separately:

• PC-600 — −196 to 150 °C (−321 to 302 °F)
• CC-33A — −196 to 120 °C (−321 to 248 °F)
• EP-340 — −55 to 150 °C (−67 to 302 °F)
• CC-35 — −30 to 120 °C (−22 to 248 °F)
• CC-36 — −30 to 100 °C (−22 to 212 °F)

Configuring the right gage

Four selections resolve a KFGS part number:

• Pattern matches the measurement application.
• Gage length matches the kind of material and the space available.
• Resistance matches the measurement application: 60 Ω for bending compensation, 120 Ω for general-purpose strain measurement, and 350 to 1000 Ω for transducers.
• Linear expansion code matches the test material.

Combinations of codes are limited, so not every pattern, length, resistance, and expansion code can be ordered together. Configure the gage on this page and buy it directly. If you need something the configurator does not cover — a combination that isn't offered, adhesive and installation accessories on the same order, or a gage manufactured to your own measurement purpose — contact us.

The KFGS cannot be used in hydrogen environments. After opening, store gages in a dry environment such as a desiccator, and wear protective glasses when bonding to prevent adhesive entering the eyes. Published characteristics are reference values and will vary with operating conditions such as the temperature effect; to increase measurement accuracy, run a pretest on the actual equipment and compensate based on the result.