10Pcs BF350-3AA BF350 350 ohm High-Precision Pressure Resistance Strain Gauge

I used these strain gauges to sense the bending of a 3D printed part. The package of ten all had matched resistances within 0.3 Ohm of each other as measured with my Fluke 77. If you bend them or squeeze them while measuring, you don't get good results - you have to measure them without putting pressure on the sensor - I imagine this is the problem with the other reviewers that complained about them not being well matched. They are strain gauges, if you strain them, they don't read 350 Ohms - they are not supposed to - this means that they are working.They are fragile, like any strain gauge. They chip and crack easily. This is not a defect - all strain gauges are like this - handle them carefully. I glued them to my parts with gap filling cyanoacrylate - it worked well.With a bridge circuit of 4 gauges, I was easily able to reliably detect the deflection of a 4 mm X 10 mm PETG rectangular rod. I set a dime on the rod, about 3cm from the sensors, and the sensor detected the weight of the dime easily, every time. They are well matched, super sensitive, and work well.The wires are small - if they were large, they would put strain on the sensor and mess up your readings. They are easy to solder and a soldering iron will burn away the insulation if you want shorter leads.I am happy with these strain gauges. They work as well as the ones I've paid $20 each for.

This is ok product. I don't see any problems as described in most 1 star reviews.I tested the resistance on multiple samples with a portable multimeter (~350.1 ohms) and a high precision multimeter (350.4 ohms). The resistance doesn't vary significantly.By adhering the gage using glue like epoxy it is very well stable when tested and gives good sensitivity.But this should always be combined with a Wheatstone bridge when using a commercial level multimeter. Otherwise direct resistance measurement will give at least 5.35% relative error of the final strain result not considering solder point resistance and wire resistance which will yield in even more error.One thing to point out, the wire is enameled only leaving a tiny end that is still conductive therefore do give difficulties when soldering into a circuit but its doable, this is something needs to be improved.Another thing is that provided gage factor is wired, it gives 2.0-2.2 on amazon website and 2.1 on the data sheet picture. This will make calculation inaccurate, constantan material should usually has a value close to 2.0 a value of 2.1 is of a bit concern. if Possible please update the gage factor.Overall this is a decent amateur level strain gage with ok sensitivity and minor problem over soldering and gage factor.

As described

It's very hard to get a sense of the size and quality from the images online. These were not what I was expecting. Previous strain gauges I ordered were completely flat. These are soldered in place so there are bumps and ridges I can't really use for this application

The wire is very small and hard to solder

If you are getting these to do ECE homework, make sure you have a digital multimeter, because the resistance readings are inconsistent.