KFH-Rosette

Supported Applications

The Omega KFH Series consists of pre-wired strain gages designed for static and dynamic strain measurement. These sensors are engineered to eliminate soldering at the measuring point, facilitating installation on test specimens. The series supports linear patterns as well as planar configurations including X-Y and 0°/45°/90° rosette patterns.

Operating Conditions & Performance

The KFH Series operates within a temperature range of -10 to 155 °C (-14 to 320 °F) for both static and dynamic measurements. The measuring grid is constructed from Constantan with thicknesses of either 3.8 μm (150 microinch) or 5 μm (197 microinch), depending on the strain gage type, mounted on a rugged polyimide carrier.

Performance specifications include:

• Gage Factor Tolerance: ±1% for grid lengths of 0.6 mm and 1.5 mm; ±1.5% for other grid lengths.
• Mechanical Hysteresis: 1 μm/m (microstrain) at the 1st load cycle using adhesive SG496, improving to 0.5 μm/m (microstrain) at the 3rd load cycle with the same adhesive.
• Fatigue Life: Greater than 1 x 10⁷ cycles tested at alternating strain Lw = ±1000 μm/m and zero point variation ≤ 300; or 5 x 10⁶ cycles with zero point variation ≤ 30.
• Maximum Elongation: Absolute strain value of 20,000 ± 2% for the positive direction and 25,000 ± 2.5% for the negative direction (measured on linear 3 mm 120Ω gage at reference temperature).

Models are compensated for steel with a nominal resistance of either 120 Ω or 350 Ω.

Configuration Options

The series offers extensive configuration options across grid patterns, dimensions, and lead arrangements to accommodate specific measurement geometries.

• Gage Patterns: Available in linear (C1), planar X-Y (D16), and planar 0°/45°/90° rosette (D17) configurations.
• Grid Lengths: Linear gages range from 0.3 mm to 20 mm; planar patterns are available in grid lengths of 0.6 mm, 1.5 mm, 3 mm, and 6 mm.
• Nominal Resistance: Options include 120 Ω or 350 Ω depending on the specific gage model.
• Electrical Connections: Pre-wired with PTFE wire (Ø - 0.051 mm², approximately 50 mm long) connected to AWG 28 ribbon cables (PVC insulated) through solder sleeves in either 2- or 3-wire configurations.
• Lead Lengths: Configurations include two 1 m leads or three 3 m leads per grid, as indicated by the model number suffixes.

Bonding materials supported by the series include cold cure adhesives (SG496 methyl-based cyanoacrylate and SG401 ethyl-based cyanoacrylate) or heat cure adhesive kits (TT300).

Key Product Differences

Variants within the KFH Series are distinguished by their gage pattern, grid length, resistance value, and lead termination style. The model number follows the format KFH----.

• Linear Pattern (C1): Models such as KFH-03 through KFH-20 offer grid lengths from 0.3 mm to 20 mm, primarily in 120 Ω resistance with options for two or three leads.
• Planar X-Y Pattern (D16): Models such as KFH-06 through KFH-6 provide orthogonal measurement grids ranging from 0.6 mm to 6 mm, available in both 120 Ω and 350 Ω resistances.
• Planar Rosette Pattern (D17): Models such as KFH-06 through KFH-6 feature a 0°/45°/90° arrangement for multi-directional strain analysis, with grid lengths from 0.6 mm to 6 mm and resistance options of 120 Ω or 350 Ω.

Maximum permitted bridge energizing voltage (VRMS) varies by model and dimensions; specific values are listed in the specification tables for each pattern type, ranging from approximately 4.8 VRMS to higher voltages depending on grid size and resistance.