Hey guys, let’s cut to the chase – if you’re here because you’re working with force sensors, testing their performance isn’t just a checkbox. It’s make-or-break, right? I’ve been in the force sensor game for over 8 years, running a small supply shop (yep, just me and a tiny team of engineers) that sends sensors out to everyone from robotics startups to medical device makers. And let’s be real – I’ve seen what happens when someone skips proper testing: a robot arm crushes a part, a prosthetic hand doesn’t grip right, even lab data that’s supposed to be exact goes all wonky. So today, I’m breaking down exactly how we test these bad boys before they leave our warehouse, no boring jargon, just real stuff that works. Force Sensor
First, let’s get one thing straight: force sensors aren’t one-size-fits-all. The type you’re testing – whether it’s a load cell for heavy industrial work, a tiny FSR for soft robotics, or a piezoelectric sensor for dynamic impact – will change your test setup. But there are core steps we use for every sensor that never fail, so stick with me.
The first and most basic step I always nail down is calibration test. Wait, I know what you’re thinking – “calibration is just lining numbers up, duh.” But no, it’s way more than that. For our sensors, we use a traceable reference force standard – like a dead weight tester, no fancy lab stuff here, just calibrated weights that are proven accurate by national metrology bodies. Here’s how we do it: hook the sensor up to our data logger, zero it first (super important – if you skip zeroing, every reading’s off by a little), then apply known weights in increasing increments. For example, if we’re testing a 0-100N load cell, we go 10N, 20N, all the way up to 100N, log each reading, then do it in reverse too (100N, 90N…10N) to make sure it doesn’t drift. Then we plot that data – if the line’s straight (linear, basically), that’s good. If there’s a curve or a gap? Dump it, no exceptions. Last month, we had a batch of tiny FSRs that showed a 2% gap at 50N, so we sent ‘em back to the manufacturer (yeah, we test our own suppliers too) and fixed it before shipping – that saved us a headache later. Pro tip: do this at least 3 times, over different days, because temperature can mess with results. We test our sensors at 20C, 25C, even 30C to account for that, especially for outdoor use cases.
Next up, accuracy and resolution testing. These two get mixed up all the time, so let’s clarify. Accuracy is how close the sensor’s reading is to the actual real force. Resolution is the smallest change in force it can pick up. Let’s say you have a sensor that reads 1N for every small tap – that’s 1N resolution. If it’s actually 0.5N off every reading, that’s accuracy error. How do we test both? After calibration, we apply a super specific, tiny force increment – like 0.1N increments for a high-res sensor – and see if the output matches. For industrial load cells, we let a 1N error slide for heavy loads, but for medical sensors that measure how much pressure a hand exerts on a surgical tool? 0.05% error max. Last year, a client came to us with a sensor they bought elsewhere that claimed 0.1N resolution, but when we tested it, it only jumped every 2N – that’s why proper testing matters, not just the specs on the box. Also, for resolution, make sure you test at different parts of the sensor – some FSRs have a “sweet spot” in the middle that’s more accurate, so you don’t want to use the edges for precise work.
Then there’s repeatability and hysteresis – two more terms that sound fancy but are dead simple to test. Repeatability is: if you apply the exact same force 10 times, do you get the exact same reading every time? Hysteresis is: if you apply force and then release it, do you get the same reading when you’re going up vs down? For example, if I push a sensor to 50N, get 50.2N, then let go and push back to 50N and get 50.8N – that’s hysteresis. We test these by cycling the load like crazy – up, down, up, down, like 50 times in a row – then check the spread. Our rule: if more than 2 out of 50 readings are off by more than our spec, the sensor’s bad. I once had a batch of piezoelectric sensors that had 8% hysteresis – turned out the adhesive between the force element and the wiring was bad, so we reworked all of them and fixed it. Repeatability’s even more important for stuff like assembly lines, where the same force is applied hundreds of times a day – if the sensor’s reading changes randomly, the line will mess up parts all day.
Dynamic performance testing is next, and this is the part that trips up a lot of people who only test static forces. Like, if you’re using a force sensor for a impact test, or a robot that’s moving fast, static calibration won’t cut it – you need to test how it handles rapid changes in force. How do we do that? We use a drop test rig or a shaker table. For example, for a sensor that’s used to measure how much force a golf club hits a ball with, we mount the sensor on a rigid plate, drop a weighted pendulum onto it at different speeds, and log the force over time. We check for things like peak force accuracy, rise time (how fast the sensor picks up the force when it’s applied), and settling time (how long it takes to get a stable reading after the force is applied). Last quarter, a robotics client came to us because their force sensor was crashing their gripper – turns out the rise time was too slow, it took 10ms to register the force, and the gripper was moving way faster than that. So we swapped them for a higher-speed dynamic sensor, and that fixed the whole issue. Also, for dynamic testing, we test at different frequencies – if the sensor’s for something vibrating, like a engine mount, we test it at the frequency the engine runs at to make sure it doesn’t resonate.
Don’t forget environmental testing, either. Force sensors don’t live in a perfect lab – some go in factories with dust, some go underwater, some get left in the sun all day. We test for that too. For temperature, we put sensors in an environmental chamber that swings from -40C to 80C, test their output at every 10C mark, and make sure the error doesn’t exceed our spec. For humidity, we blast them with 95% humidity at 40C for 100 hours, to make sure no moisture gets in and shorts the wiring. We even test dust and water resistance – if a sensor’s rated IP67, we submerge it in 1m of water for 30 minutes, then test it. One client makes agricultural equipment that works in mud and rain, so we test all their sensors to be IP68, no exceptions. We also test for vibration – mount sensors on a shaker table with different vibration frequencies and amplitudes, make sure the readings don’t drift. Last year, a wind turbine client had sensors that failed after 6 months because of vibration, so we added a reinforced wiring connector to our design, and now those never fail.
Wait, what about cross-sensitivity? That’s a big one I almost forgot. Cross-sensitivity is when the sensor picks up force from directions other than the one it’s supposed to measure. Like, a load cell that’s supposed to measure vertical force, but also picks up side force from the load pushing sideways. That’s a problem because it skews readings. How do we test that? We mount the sensor in a way that lets us apply force in x, y, z directions separately. Apply 100N of vertical force, then apply 10N of side force, and see how much the reading changes. Our specs say cross-sensitivity has to be less than 1% – so if a sensor’s main reading is 100N, it can’t show more than 101N when we apply that side force. We had a batch of low-cost load cells a while back that had 5% cross-sensitivity, so we dumped that supplier and found a better one – worth paying a little more for consistent results.
Now, let’s talk about how we do all this without breaking the bank. You don’t need a $1M lab to test force sensors, trust me. We use off-the-shelf data loggers, calibrated weights from a local metrology shop, and a custom test rig we built in our garage (literally, my engineering buddy and I welded it together in 2021). For dynamic testing, we use a motorized arm that can apply controlled force at different speeds, no fancy shaker table needed. The only thing you really need is a way to log data accurately and a way to apply controlled forces. If you’re just starting out, don’t overcomplicate it – start with calibration and repeatability tests first, then add dynamic and environmental as you go.
Here’s the thing I want you to take away: testing force sensors isn’t about checking boxes. It’s about making sure your project works, no surprises. Whether you’re a engineer building a new robot, a lab tech running experiments, or a manufacturer making medical devices, your force sensor’s performance only as good as your testing. And if you’re tired of sensors that fail mid-project, give us a shout – we don’t just sell sensors, we test every single one before it leaves our warehouse, so you don’t have to. We can work with you to customize tests for your use case, help you pick the right sensor, and make sure it works exactly how you need it to.
Last notes: don’t skip zeroing the sensor before every test, even if you just used it 5 minutes ago. Small drifts add up. And always log all your test data – even if a sensor passes, save that data, so if something goes wrong later, you can look back and see when it started failing. We keep test data for every sensor we’ve sold for the last 5 years, just in case a client has an issue. That’s the kind of reliability you get when you test every step, not just send products out the door.
Weighing Transmitter References:
- ISO 376:2011, Metallic materials – Calibration of force-proving instruments used for the verification of uniaxial testing machines
- Walker, D. C., "Force Sensor Performance Testing: A Practical Guide", Journal of Sensor Technology, vol. 8, no. 2, pp. 45-52, 2020
- ANSI/ISA-99.00.02-2013, Security for Industrial Automation and Control Systems – Part 2: Security Integrity Levels for Industrial Control Systems
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