Best Practice Guide: Preparing and Installing a Strain Gauge

A strain gauge installation is only as good as the bond between the gauge and the test surface. Most issues drift, noise, unstable readings, early failure come from surface contamination, poor bonding technique, weak strain relief, or inadequate protection.

This guide outlines a proven, industry standard workflow for installing bonded foil strain gauges. Always follow the instructions for the specific adhesive/coating system you’re using, but use the steps below as your best practice baseline.

What You’ll Need

Typical tools & consumables

Lint free wipes / swabs
Approved degreaser/solvent for your substrate
Fine abrasive paper (or controlled abrasion method)
Clean handling tape (for positioning)
Correct adhesive for your material, temperature, and environment
Soldering iron, solder, suitable flux (as required), and flux remover
Lead wire and strain relief materials (tape, adhesive fillet, protective overcoat)
Multimeter or strain indicator (for basic electrical checks)

Step 1: Choose the Right Location and Orientation

Pick a location representative of the strain field (avoid edges, sharp corners, deep scratches, corrosion, or poorly bonded coatings unless your test demands it).
Align the gauge grid with the primary strain direction.
If strain direction is unknown or multi-axial, consider rosettes.
Plan lead routing so wires don’t pull on the gauge area and so you have room for protection layers.

Step 2: Surface Preparation

(Most Important Step)

Surface prep is where installs succeed or fail. The goal is a clean, fresh, uniform surface that allows intimate contact with the gauge backing.

Best practice surface prep workflow

Degrease the area thoroughly (remove oil, fingerprints, coolant residue).
Lightly abrade to create a uniform finish and remove oxides/weak surface layers.
Clean again to remove all dust and abrasive debris.
Final wipe with fresh lint free wipes until no residue is visible.

Key rules

Don’t touch the prepared surface with bare fingers.
Use fresh wipes/swabs re-using a contaminated wipe just spreads residue.
Keep prep and installation tools clean and dedicated where possible.

Step 3: Dry Fit and Mark Alignment

Mark a light alignment reference (avoid deep scribes).
Do a dry fit for orientation and lead routing.
Prepare your handling tape “hinge” so the gauge can be placed accurately without sliding.

Step 4: Handle the Gauge Correctly

Avoid touching the bonding side of the gauge.
Keep the gauge protected from dust until the moment you bond it.
Ensure the gauge lies flat and isn’t creased or stressed during handling.

Step 5: Bonding the Strain Gauge

Choose an adhesive based on:

Substrate (steel, aluminium, titanium, composites, plastics)
Temperature range (ambient, elevated, cycling)
Environment (humidity, splash, immersion, oils/chemicals)
Install speed (fast turnaround vs longer-cure systems)

Bonding best practices

Apply a controlled, thin bond line (too much adhesive increases creep and instability).
Place the gauge using your tape hinge to avoid sliding.
Apply even pressure during cure (as recommended by your adhesive system).
Allow full cure before soldering, tugging lead wires, or coating.

Tip: Avoid overheating the gauge area during any heat-cure process. Uneven heating can lead to bubbles or weak bond zones.

Step 6: Wiring and Soldering

Good wiring is about repeatability and mechanical stability.

Best practices

Use a clean, temperature-controlled iron where possible.
Keep solder joints small, smooth, and well wetted.
Minimise dwell time (don’t “cook” the pads).
After soldering, remove flux residue using a suitable cleaner for your system.

Use terminal pads when appropriate
For many builds, soldering lead wires to a bondable terminal pad (instead of directly at the gauge) can make wiring cleaner and reduce mechanical stress at the gauge. This is especially useful when cables are heavier, routing is tight, or vibration is present.

(MFL Strain Gauges manufactures copper bondable terminal pads on both polyimide and epoxy backing, depending on the durability/flexibility you need.)

Step 7: Add Strain Relief (Do Not Skip)

Strain relief stops lead movement from stressing the solder joints and gauge area.

Common approaches:

A small, flexible adhesive fillet over the first section of wire
Taping down the wires a short distance away from the gauge
Routing wires so they don’t snag or vibrate

Step 8: Verify Before Protection

Before applying protective coatings, do quick checks:

Visual inspection: gauge flat, aligned, no obvious trapped debris or lifted edges
Resistance check: confirm the gauge reads close to its nominal resistance
Insulation/isolation check: ensure the installation isn’t shorting to the specimen (method depends on your instrumentation)

If something is off, it’s far easier to fix now than after encapsulation/protection.

Step 9: Environmental Protection and Encapsulation

Protection choice depends on the real environment:

Humidity/water exposure
Temperature cycling
Oils/chemicals
Mechanical impact risk

A typical order of operations is:
wire → clean → strain relief → protective coating/encapsulation

If your application is harsh or long-term, plan protection from the start (including cable jacket choice and sealing edges).

Common Mistakes That Cause Bad Data

Rushing surface prep or leaving abrasion dust behind
Touching the prepared surface or gauge backing
Using too much adhesive (thick bond line)
Moving wires without strain relief
Coating before verifying electrical checks
Using adhesives/coatings outside their rated environment

Need Help Choosing the Right Setup?

If you tell MFL Strain Gauges:

material and surface condition
temperature range
environment (dry, humidity, splash, immersion, oils)
gauge type (linear / shear / rosette / full bridge)
cable routing constraints

…we can recommend a practical installation approach.