Strain Gage Installation

 

Strain Gage Installation Instructions

1. Prepare shaft surface:

  • Remove paint and other coatings; degrease as necessary.
  • Rough sand with 220 grit paper then polish with 400 grit paper.
  • Finish sanding with 400 grit paper and M-Prep Conditioner.
  • Rinse with M-Prep Conditioner.
  • Rinse with M-Prep Neutralizer and wipe dry.


2. Mark shaft surface for strain gage orientation and alignment. 

  • The strain gage should be installed flat and square to the axis of the shaft.  For a straight reference line square to the axis, wrap a piece of paper around the shaft, align the edges and then mark or etch the straight reference line onto the shaft.


3. Prepare strain gage for mounting. 

  • Part # CEA-06-250US-350 is a common torque-pattern strain gage.
  • Remove strain gage from package.
  • Apply cellophane tape to top side of gage.  Use the tape as a “handle.”


4. Position strain gage before gluing:

  • Tape gage in place on the shaft using reference marks on shaft and gage for alignment.
  • Lift one end of tape and “hinge” back to expose bottom of gage.
  • Apply an even, thin layer of catalyst to bottom side of gage and let dry.


5. Glue strain gage to surface:

  • With the gage/tape still hinged back, apply bead of M-Bond 200 Adhesive where the tape meets the shaft surface.  (M-Bond 200 is a special Cyanoacrylate which has been pretested and certified for use in bonding strain gages – manufactured by Vishay Measurements Group.)
  • Using Teflon film or equivalent as a non-stick barrier between your thumb and the adhesive, press the gage/tape to shaft surface with single rolling/wiping motion of the thumb.
  • Apply thumb pressure for one minute, followed by a minimum two-minute wait before removing the cellophane tape. Bond strength increases rapidly during first five minutes.


6. Attach lead wires and protect strain gage:

  • Discard Teflon film and carefully peel back cellophane tape from the strain gage.
  • Tin with solder the solder pads of the strain gage plus the lead wires.  Attach lead wires to solder pads.
  • Clean solder joints with rosin solvent.
  • For waterproofing – Apply polyurethane coating to strain gage and solder joints.
  • For mechanical protection – Cover the gage with butyl rubber or equivalent.
  • For electrical shielding – Cover the strain gage and lead wires with aluminum tape or equivalent.
  • M-Coat J from Vishay Measurements Group is a two-part polysulfide liquid polymer compound for environmental protection of strain gage installations.  When fully cured, it forms a hard rubber-like covering that provides an effective barrier against water and many other fluids. The tough coating also protects installations from mechanical damage.


7. Strain gage wiring diagram:

Strain Gage Wiring Diagram