How to attach the sensor to a specimen?

The “right” way depends on the sensor type, specimen material, frequency content, environment, and whether the mount should be temporary or permanent. Here’s a compact playbook you can follow right away.

Quick decision guide

• Need high bandwidth / precision (strain, vibration)? → Rigid bond (thin cyanoacrylate or epoxy) or stud/screw mount on a machined flat.
• Thermal sensing (thermocouple/RTD) where mass matters less? → High-temp epoxy or Kapton® tape + thermal grease; metals can also be spot-welded (TC only).
• Temporary tests / delicate surfaces? → Wax (beeswax/mounting wax), double-sided acrylic tape, removable putty, or magnetic/vacuum fixtures (if compatible).
• Soft/biological or curved parts? → Silicone RTV or flexible tape + strain relief; use skin-safe adhesives for humans/animals.
• Wet/corrosive/outdoor? → Epoxy bond + edge sealant; consider conformal coat or heat-shrink boot.

Universal steps (works for almost any sensor)

1. Define the point & axis you want to measure; mark alignment lines (for strain/accel orientation).
2. Surface prep: degrease (IPA), lightly abrade (600–1200 grit) if allowed, clean again, and dry. For plastics that hate solvents (PC, ABS), skip acetone; use IPA only.
3. Dry fit the sensor; ensure full contact and a flat seat.
4. Bonding/fixture: apply the thinnest practical layer; press with firm, even pressure. Avoid squeeze-out onto leads.
5. Cure / set: hold per adhesive datasheet (pressure/temperature/time).
6. Strain-relieve the cable: loop + tape/epoxy 2–3 cm away so motion doesn’t load the sensor.
7. Verify: check resistance/offset, tug-test the lead, then calibrate/zero.
8. Protect: edge-seal (strain gauges), conformal coat, or shield as needed.

Sensor-specific playbooks
1) Strain gauge

• Adhesive: thin cyanoacrylate (fast tests) or two-part epoxy (stable, high-temp).
• Procedure: prep → align to principal strain → tiny CA drop → squeegee thin bond → hold ~1 min (CA) or cure epoxy → edge-seal → solder tabs → cable strain relief → bridge balance & temp comp.
• Tip: keep bond line as thin as possible; thick glue = compliance error.

2) Thermocouple / RTD

• Metal specimen: best is spot weld the TC bead; otherwise high-temp epoxy or Kapton tape + thermal grease (fast response, removable).
• Non-metal: epoxy or silicone RTV; tape for temporary.
• Tip: minimize bead mass and insulate leads from drafts; for surface temp accuracy, cover with a small square of tape/foil.

3) Accelerometer

• Mount: stud/screw to a machined flat is ideal; next best is hard epoxy or wax (for temp jobs).
• Surface: flat within ~0.05 mm, smooth, clean.
• Tip: keep sensor mass small relative to local structure (rule-of-thumb: <5% mass loading). For high-freq work, use rigid mounts and a very thin adhesive layer.

4) Pressure sensor (surface or tubing)

• Contacting diaphragm to surface/medium: use the manufacturer’s adapter; avoid smearing epoxy over the pressure port.
• Tubed pressure: barbed fittings + clamps; add strain relief; avoid sharp bends near the port.

5) Displacement/optical (DIC, laser, LVDT target)

• Targets: matte-white + speckle (for DIC) or reflective tape (laser).
• Mounts: small brackets epoxied/screwed to the specimen; keep bracket stiffness high and mass low.

Specimen material tips

• Aluminum/Steel: abrade lightly; acetone/IPA clean; (TC) spot-weld okay.
• Composites (CFRP/GFRP): avoid deep sanding into fibers; use epoxy; seal edges.
• Plastics (ABS, PC, PLA): no acetone on PC/ABS; use IPA; silicone/epoxy with low exotherm.
• Wood/porous: seal with thin epoxy first, then bond sensor on top.

QA & troubleshooting

• Offset drift: bond too thick or still curing → re-mount thinner; allow full cure at test temperature.
• Noisy signal: cable moving → add strain relief & tape-downs; shield and twist pairs.
• Frequency loss (vibration): soft adhesive or uneven seat → switch to stud/epoxy and re-machine the pad.
• Thermal lag (TC/RTD): large bead or thick glue → reduce mass; use tape + grease.

Concrete examples

A) Strain gauge on aluminum dog-bone (tension test)
Prep (IPA → 600-grit → IPA) → align gauge along axis → tiny CA drop, squeegee thin, hold 60 s → edge-seal → solder leads → strain-relieve with tape 20 mm away → balance bridge & zero.

B) Thermocouple on steel pipe
Spot-weld bead to pipe → cover with a small Kapton square to cut convection → route and tie leads; if no welder: epoxy bead + a dab of thermal paste under bead, Kapton over.

C) Stud-mounted accelerometer on aluminum plate
Face-mill a 10 mm pad; tap M5; torque sensor to spec (with a drop of removable threadlocker); route cable with loop and tape; verify mounting resonance > test band.

Safety & compliance notes

• Follow your adhesive’s MSDS (PPE, ventilation).
• For human/animal attachment, use skin-safe adhesives/sensors and follow institutional/IRB and manufacturer guidance.