Weldable Strain Gage Installations
The vast majority of installations employ adhesive bonding, a tried and true method used since the invention of the bonded resistance strain gage in 1936. Micro-Measurements offers an extensive line of adhesives that perform well in a myriad of applications, including those exposed to extreme operating temperatures—from deep cryogenic up to 800 °F.
There are instances, however, where adhesive bonding is just not an option. For example:
- Steel bridge sections in cold environments or difficult-to-access locations
- Ship hulls in very humid or wet environments
- High-temperature applications above 700 °F
- Test specimens that can’t be taken offline for gage installation
In such cases, welding a gage in place is often the best solution. Micro-Measurements offers a range of weldable devices, including sealed versions with pre-attached cables for wet environments; open-tab versions to accommodate installation of lead wires; and high-temperature versions free of organic materials for operation up to 1800 °C.
So, is this installation technique difficult to learn? Not at all. In fact, surface preparation is nearly identical to bonded gages. Typically, a technician experienced in strain gage bonding can perfect the welding technique in less than an hour.
Our weldable gages are provided on an Inconel or stainless steel shim to allow for spot welding. To facilitate installation, the Model 700 Portable Strain Gage Welding/Soldering unit enables capacitive discharge welding and features an onboard soldering pencil for lead wire attachment. The Model 700 includes a charging unit and can be placed in a backpack to free up technicians' hands.
There are a number of other advantages in using weldable gages:
- Bonding to the shim is performed under ideal conditions to ensure proper adhesion
- Fast installation with no adhesive cure time required
- Installations are compatible with most conventional protective coatings
- Testing can often begin immediately
So is a weldable gage the best choice for every application? Of course not. Welding is only an option on compatible materials, and the accuracy and fatigue life of a bonded gage is superior. However, when adhesive bonding is not an option, a weldable gage may be the best—and sometimes only—solution.