Standard strain gauges

Depending on the version, strain gauges are available either without cables or with factory-fitted lead wires. Common cable lengths are 1 m, 3 m, and 5 m, while very fine enamelled wires are typically available in lengths of 0.3 m, 0.5 m, or 1 m. Custom lengths may also be available depending on the strain gauge type.

Available options include vinyl-insulated, shielded, moisture-resistant, and temperature-resistant cables, as well as fine enamelled wires. Depending on the application, 2-wire or 3-wire connections can be used. A 3-wire configuration is particularly advantageous for longer cable runs or varying temperatures because it helps reduce the influence of lead wire resistance on the measurement.

Althen can support the selection of the appropriate cable type, cable length, and connection method based on factors such as temperature, moisture, electrical interference, and the distance to the measuring amplifier.

Delivery times for strain gauges depend on the selected series, grid pattern, resistance, cable type, and connection configuration. Standard versions are generally available sooner than special strain gauges, custom versions, or products with pre-assembled lead wires.

The exact lead time therefore depends on the specific strain gauge and the required quantity. Althen can help select a technically suitable strain gauge with the shortest possible delivery time.. Althen can help select a technically suitable strain gauge that is available as quickly as possible.

No. Bonded strain gauges are generally designed for single use. Once bonded, the strain gauge and adhesive form a permanent connection to the component surface, ensuring that the strain is fully transferred to the measuring grid.

Removing the strain gauge will usually damage the backing, measuring grid, or lead wires. Adhesive residue can also affect the measurement characteristics.

A new strain gauge should therefore be used for each new measuring point. Weldable strain gauges are also typically intended for permanent installation and should not be reused after removal.

For reliable strain measurement, a strain gauge must be attached to the component surface using the correct preparation and bonding procedure. The installation area should first be cleared of paint, rust, grease, and other contaminants, then lightly abraded and thoroughly cleaned with a suitable solvent.

A suitable strain gauge adhesive should be applied in a thin, even layer. The strain gauge is then positioned accurately in the required measurement direction and bonded evenly to the surface without air bubbles for the specified curing time. After curing, the lead wires should be strain-relieved, connected to terminal pads, and carefully soldered.

The choice of adhesive and, where necessary, protective coating depends on the material, temperature range, measurement duration, and environmental conditions. A detailed step-by-step guide covering surface preparation, bonding, and wiring is available from Althen: How to attach a strain gauge correctly.

For most standard TML strain gauges, a standard pack contains 10 pieces. For the F series, for example, both the pack quantity and the minimum order quantity are 10 strain gauges.
For special designs, such as weldable strain gauges, multi-grid versions, or strain gauges for specific applications, the number of pieces per pack may vary. The exact quantity depends on the product series and full type designation. Althen will confirm the applicable pack quantity when preparing a quotation.

"The shelf life depends on the specific adhesive. For the strain gauge adhesives offered by Althen, the specified storage life is typically 3 or 6 months. For example, CN, CN-E, CN-Y, P-2, and NP-50B have a shelf life of six months, while CN-R, RP-2, EA-2A, C-1, EB-2, and A-2 typically have a shelf life of three months.

Proper storage is essential. The adhesive should be kept in a cool, dry, and dark place, preferably refrigerated at +5 to +10 °C. It must not be frozen. Always follow the expiry date and storage instructions stated on the packaging or in the data sheet."

For strain measurement on steel, standard F-series strain gauges are suitable for many applications. An important factor is that the strain gauge temperature compensation is matched to the coefficient of thermal expansion of the steel. Strain gauges with the designation “11” are commonly used for this purpose, corresponding to a coefficient of thermal expansion of approximately 11 × 10⁻⁶/K.

The right version also depends on the measurement direction, measuring-point geometry, temperature range, moisture exposure, and expected strain. For standard environmental conditions, linear F-series strain gauges are generally suitable. Where moisture, high temperatures, or difficult-to-access measuring points are involved, waterproof, temperature-resistant, or weldable versions may be more appropriate.