If you’ve ever shopped around for load cells—especially if you’re working in manufacturing, packaging, or material testing—you’ve almost certainly run across S-type load cells at some point. They’re one of the most common load cell designs on the market, and for good reason: their distinctive S shape makes them easy to integrate into existing setups, they come in a huge range of capacities, and they’re known for being cost-effective and reliable for a lot of tension measurement applications. But over the years, I’ve lost count of how many times I’ve gotten a call or an email from someone asking me a pretty basic, but surprisingly tricky question: “Can your S-type load cell actually be used for compression, or am I stuck buying a different unit?” As a supplier who’s built my business on answering these kinds of practical, real-world questions instead of just pushing my products, I’ve spent a lot of time talking through this with engineers, production supervisors, and small business owners, and I figured it was time to put all that context out there to clear up the confusion once and for all. S Type Load Cell
First, let’s start with the basics so we’re all on the same page. An S-type load cell gets its name from its shape— a central body with two threaded ends sticking out, forming a capital S when viewed from the side. Internally, most S-types are strain-gauge-based, which means they use tiny, very precise gauges that change resistance when they’re stretched or squeezed. For decades, the primary job these units were designed for is tension measurement: pulling force, like when you’re testing how much a rope or a cable can hold before it breaks, or checking the tension on a conveyor belt in a warehouse. That’s why most datasheets you’ll find online for S-type load cells will lead with tension as their intended application, and it’s easy to assume that means they can’t do compression at all. But that’s not the whole story.
The key here is how strain gauges work and how they’re installed inside an S-type load cell. Strain gauges only measure force if they’re properly aligned with the direction of that force. For tension, the load pulls on both ends of the S shape, stretching the central section of the cell where the gauges are mounted, which registers as a signal that corresponds to the amount of pull. For compression, you’d think squeezing both ends would also stretch or strain the gauges, right? Well, that’s only partially true. If you apply compression force directly along the line of the S’s axis, the central section does actually deform—but it’s a very different kind of deformation. Most standard S-type load cells have their gauges wired in a Wheatstone bridge configuration that’s calibrated specifically for the stretching force of tension. That means they’re not set up to pick up the subtle strain from compression without a lot of extra noise or inaccurate readings.
But here’s the part most people don’t know: modern S-type load cells can absolutely be adapted for compression measurement, as long as you make a couple of small, intentional modifications. I’ve seen this work successfully in dozens of applications over the years—from packaging lines checking that boxes are sealed to the right tightness to material testing labs running compression tests on small samples. Let me break down what that actually looks like in practice, because it’s not just a “flip it over and go” trick.
First, the easiest and most common way to use an S-type for compression is to install it backward in your setup. Wait, that sounds backwards, but hear me out. Normally, you connect one end of the S load cell to a fixed point and the other to whatever you’re pulling, so the force pulls the cell apart. If you instead fix both ends to fixtures that push toward each other (so the force squeezes the entire S shape together), the gauges will register that compression force—but only if your load cell has been designed to handle that bidirectional force. Not all S-types can do this, though. Standard tension-only S cells have thinner, more delicate central sections that will buckle or get damaged if you apply too much compression, because they weren’t engineered to handle that sideways or squeezing force. That’s why it’s critical to specify a bidirectional S-type load cell when you’re ordering, instead of a standard tension-only model. I always tell customers who ask about compression to make this distinction first: check the datasheet for a “compression capacity” rating in addition to the standard tension capacity. For example, a common 500kg S-type might have a tension rating of 500kg and a compression rating of 300kg, so you know it’s safe to squeeze it up to that 300kg limit without damaging it.
Another trick I’ve passed on to smaller manufacturers who don’t want to upgrade their entire setup is adding custom fixtures to the ends of the S-type to distribute the compression force evenly. S load cells have small, threaded ends, and if you just push directly on those ends, you might get uneven force that causes the cell to twist slightly, which throws off the readings and can even damage the unit over time. I’ve seen customers machine simple aluminum pucks that fit over each end of the S, creating a flat, even surface to apply compression force across. This not only gives you more accurate readings but also extends the life of the load cell, because it prevents the sharp threads or small contact points from putting stress on the internal strain gauges. This is a low-cost fix that works surprisingly well for low-capacity compression applications—no need to buy a whole new load cell design if you don’t have to.
Now, I’d be doing my customers a disservice if I didn’t be honest about the limitations here. S-type load cells aren’t the best choice for every compression measurement job, and there are scenarios where you’re way better off buying a dedicated compression load cell. For example, if you’re working with very high compression forces—like hundreds of thousands of pounds in heavy industrial material testing—S-types aren’t usually designed for that kind of load, even as bidirectional units. Dedicated compression load cells, often called pancake load cells or compression buttons, are built specifically to handle uniform compression force at much higher capacities, and they’re more accurate for that exact use case. Also, if you need extreme precision—like in a lab testing micro-force compression on small medical devices—standard S-types might have more cross-talk (that’s when the cell picks up force from directions other than the one you’re measuring) than a dedicated compression unit. Cross-talk is a big issue with S-type cells when used for compression, because their S shape is inherently a bit more flexible along other axes than a pancake compression cell, so you have to account for that in your setup by eliminating any side-to-side or twisting forces as much as possible.
I also want to talk about a common mistake I see all the time: people trying to use an S-type load cell meant only for tension for compression without checking its ratings. I once had a customer a few years back who bought 10 standard S-types for a packaging line project, flipped them around to use for compression sealing, and burned through three of them in a week. When they called me frustrated, I walked them through what happened: those units were rated for only tension, so applying even a small compression force above what the threads could handle damaged the internal strain gauges, making the readings totally inaccurate. That’s why I always emphasize that if compression is even a possibility for your application, you should specify a bidirectional S-type at the time of ordering. It’s not a huge extra cost—usually just a 10 or 15% premium over a standard tension-only S-type—and it saves you the headache of broken units and lost production time.
Another area where S-type load cells work really well for compression is in retrofits. A lot of older production lines were built with tension measurement setups, and switching to a different load cell design would require reconfiguring mounts, wiring, and software. Because S-types use standard threaded ends and fit into almost any existing load cell mounting, they’re perfect for these retrofits. I had a customer in the automotive parts industry a couple years ago who needed to add compression testing to their old stamping press, and instead of modifying the entire press, we sent them bidirectional S-type load cells that fit right into their existing tension mounts. They calibrated the system to adjust for the compression force, and they were up and running in a day, no major downtime. That’s the kind of practical benefit that makes S-types so versatile, even beyond their original design purpose.
Let’s also touch on calibration, because that’s a big part of getting accurate readings when using an S-type for compression. Every load cell needs to be calibrated to match your specific setup, and this is even more important when you’re using a unit in a way it wasn’t originally designed for. When a load cell is calibrated for tension, the calibration software is set to account for the stretching strain on the central section. When you use it for compression, that strain is compressive, so the calibration needs to be adjusted to recognize that force and convert it to the correct weight or force reading. That’s not something you can just do on your own with a phone app, usually—you either need to have a professional calibrator reset the cell’s settings, or if you’re ordering a bidirectional S-type from a reputable supplier like me, we’ll calibrate it for both tension and compression at the factory, so it’s ready to use right out of the box.
I get asked all the time: “If I can get an S-type for compression, why would I ever buy a dedicated compression load cell?” The answer comes down to use case, cost, and ease of integration. If you’re working with a small to medium compression force, you already have S-type mounts in your setup, and you don’t need the extreme precision of a lab-grade compression cell, an S-type is a great, cost-effective option. But if you’re working with very high forces, need micron-level precision, or have a setup that only uses compression, a dedicated compression cell will give you better accuracy and longer life. The key is matching the load cell to your specific needs, not just assuming one design is only for one job.
Over the years, I’ve seen the load cell industry shift a lot, and one of the most common myths I’ve worked to dispel is that load cells are only good for one type of force. The truth is, modern strain-gauge technology is flexible, and good design lets load cells adapt to different force directions as long as they’re engineered for it. S-type load cells are a perfect example of that: their shape makes them intuitive for tension, but with a few simple specifications and setup tweaks, they can be a reliable, cost-effective choice for compression too.
At the end of the day, I’m in this business to help my customers get the right tool for their job, not just sell them whatever’s on my shelf. If you’re wondering whether an S-type load cell will work for your compression application, my first question to you is: what’s the capacity you need? How precise do your readings need to be? Do you have existing mounts that will fit an S-type? Answering those questions will help us figure out if a bidirectional S-type is a good fit, or if you’d be better served by a dedicated compression load cell. I’ve worked with hundreds of customers to troubleshoot this exact question, and I’m always happy to walk through your specific project, share real-world examples from similar setups, and help you make the call that works best for your bottom line and your production goals.
If you’re ready to discuss your load measurement needs, no matter whether you’re looking for tension, compression, or both, please reach out to connect with our team to learn more about our range of S-type load cells, including bidirectional models calibrated for compression use. We’re here to answer your questions, share application notes, and help you find the right solution for your project.
Miniature Load Cell References
- Load Cell Fundamentals, Omega Engineering, 2022.
- Strain Gauge Technology and Application, National Instruments, 2021.
- Bidirectional Load Cell Design and Performance, Sensors Magazine, 2020.
- Industrial Load Cell Selection Guide, Automation World, 2023.
Huzhou Zhihe Technology Co., Ltd.
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