WHEN TO USE WELDABLE STRAIN GAGES
If you have always relied on adhesive bonded strain gage sensors, don’t let the title of this blog concern you. While there are other ways to adhere a strain gage to the material you are measuring, the vast majority of strain gage installations employ adhesive bonding. In fact, the adhesive bonding technique dates back to 1936 when the bonded resistance strain gage was invented. It’s simple and it works (most of the time). Micro-Measurements offers an extensive line of adhesive strain gages that perform well in a myriad of applications. Some adhesives can even operate when exposed to extreme operating temperatures—from deep cryogenic all the way up to 700 °F. This tried-and-true method isn’t going anywhere.
Adhesive Strain Gage vs Weldable Strain Gage
Despite the versatility and variety of adhesives, there are instances where adhesive bonding just doesn’t work. In these cases, you need an option that will guarantee your strain gage can function properly and remain bonded to whatever material is being tested. Here are several examples of situations that require an installation method other than adhesive bonding:
• 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, the best solution is often to weld the gage in place. If done properly, welding a gage in place offers a secure bond with no real downside. Micro-Measurements offers a range of weldable devices, including sealed versions with pre-attached cables for wet environments and open-tab versions to accommodate installation of lead wires. If you are measuring a material in an extremely high-temperature environment, we have you covered there, too. We carry high-temperature weldable strain gages that are free of organic materials for operation up to 1800 °C. Basically, if a condition exists where a strain gage is needed to perform a measurement, we have a solution.
With the adoption of any new tool, there’s always a bit of anxiety about the learning curve necessary to properly employ the tool. In the case of weldable strain gauges, you may be wondering, is this installation technique difficult to learn? Our definitive answer is, not at all. For starters, surface preparation is nearly identical to that required for adhesive gauges. Typically, a technician experienced in strain gage bonding can perfect the welding technique in less than an hour.
Perhaps you’re thinking that welding sounds tricky, especially compared to simple adhesive bonding. However, we’ve made things as simple as possible for the welder. For instance, our weldable gages are provided on an Inconel or stainless steel shim to allow for spot welding. To facilitate installation, the Model 700B Portable Strain Gage Welding unit enables capacitive discharge welding (no blowtorch necessary). The Model 700B uses standard commercially available interchangeable batteries to eliminate downtime for charging.
Technicians, just throw it in your backpack and you’re hands free.
Advantages of Weldable Strain Gages
There are several other advantages to 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
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 an adhesive strain gage are superior. However, when adhesive bonding is not an option, a weldable gage may be the best—and sometimes only—solution.
If you would like to learn more about how Micro-Measurements produces products for all conditions, here are several ways for you to keep up:
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