Applying strain gages for measurement may sound daring, but it’s a lot simpler than it sounds. In this article, we will focus on key points of strain gage placement technique. It is important that the strain gage performs well and gives an accurate reading. This means the attachment point must be performed correctly to receive good results. As a result, the strain gage setup process requires a precise and correct following of directions. Crystal Instruments’ Spider-80SG is capable of calibrating and resetting measurement values prior to taking measurement. This is a standard step for all strain measurements to eliminate any offset before measurement starts.
A. Surface Preparation
- Wipe the surface clean with alcohol or acetone.
- Wet sand the surface with fine sand paper (between 800 and 1200 grit)
- Make sure all the surface coating, if any, is removed
- Clean the surface again with alcohol and acetone.
B. Strain Gage Attachment
- Align the strain gage with the provided thin plastic. Mark the attachment location and use tape to lock the gage to its correct position. This is the only time the mounting position can be adjusted.
- Lift one side of the tape (be sure to not bend the strain gage in the process). Apply the correct amount of adhesive on the strain gage’s mounting side.
- Mount the strain gage on the surface, press a thumb down on the strain gage through the plastic sheet (mounting tape). The strain gage should come back to the exact position previously set/aligned by the mounting tape.
- Cure time is 60 seconds, depending on which adhesive is used and the strain gage manufacturer recommendation.
- Remove the mounting tape
- Use a solder tab for wire soldering to achieve good insulation from the specimen
- Apply protective coating against moisture and other contaminants
C. Cable Management
- Ensure the cable will not contribute any stress to the measurement point and secure it with tape.
- Leave a hump gap on the terminal to allow flexibility in bending movements. Flexing of the terminal also affect measurement values.