> > I think they may be bending beams and strain gauges.
Judging by the range they claim they can reach I think it's not the case. Apparently they use the compressed air as a means to sense the position of the arm. I still think RVDT could be a very good solution. I also thought about using a rotary capacitor but those are more sensitive to harsh environments and have less linearity than RVDTs apparently. El mar, 25 nov 2025 a las 11:11, andy pugh (<[email protected]>) escribió: > On Tue, 11 Nov 2025 at 01:07, andy pugh <[email protected]> wrote: > > > I think they may be bending beams and strain gauges. > > For once the AI on Google is spot on (and better than the web results) > I made a lot of these when working in the field described. (fatigue > testing of CTS specimens). > Despite being extremely simple, they are very accurate and surprisingly > linear. > > -----------------begin-AI------------------------------ > "Clip gauges" generally refers to clip-on extensometers used in > materials testing, specifically for measuring crack mouth opening > displacement (CMOD) or large strains in specimens. Fabricating one > involves installing strain gauges on a simple flexure device, which > requires specific materials and careful procedures. > Materials Needed for a Basic Clip Gauge > > Spring steel strips for the main body of the gauge. > Strain gauges (e.g., EP-series for high elongation measurements). > Terminals for wiring connections. > Connecting block for fixing the strips. > Cyanoacrylate (CN) glue for bonding the strain gauges. > Cleaning agents: sandpaper, cotton, acetone, iso-propyl alcohol (IPA). > Tools: Tweezers, low-tack cellophane tape, light scribing tool or 4H > pencil, soldering iron and wires (for connecting wires). > Calibration tools: A system for applying known displacements and > measuring the output (e.g., a comparator bar). > > Step-by-Step Fabrication Process > > Prepare the spring steel strips: Clean and abrade the areas where the > strain gauges will be installed using sandpaper. The position should > be as close as possible to the region of maximum bending stress. > Clean thoroughly: Remove all abrading debris using cotton and acetone, > then clean again with IPA. Avoid touching the prepared surface with > your fingers afterward. > Mark alignment lines: Use a light scribing tool or 4H pencil to mark > alignment lines for the gauges. > Position gauges and terminals: Use tweezers to place the strain gauges > and terminals against the alignment lines. Secure their relative > position with low-tack cellophane tape, ensuring the metal foil grid > faces up. > Bond the gauges: Roll one end of the tape back to expose the backing > sheet. Apply a small drop of CN glue to the backing sheet and stick > the tape back in place, applying even pressure. > Wire the gauges: Solder the connecting wires to the terminals. The > gauges are typically wired into a half or full Wheatstone bridge > configuration to maximize the signal. > Mount the gauge "feet": Design the device so that it can be mounted to > the test specimen by bonding or spot welding, depending on the > material. > Calibrate the finished gauge: The clip gauge is a nonlinear device and > requires calibration against known displacements before use. Monitor > the "zero" reading during calibration to check for permanent offsets, > which may indicate localized yielding. > > For a detailed guide on the design and calibration, academic resources > like the paper on the "Optimum Design of a Ring-Shaped Clip Gauge" > provide an analytical framework. > --------------------------------------------- > > > https://link.springer.com/article/10.1007/s40799-020-00417-1#:~:text=To%20design%20a%20gauge%20with,available%20in%20commercial%20mathematical%20software > . > > This video shows a completed one, but is otherwise not as good as one > might hope. > https://www.youtube.com/watch?v=5ry-7iqQIEw > > -- > atp > "A motorcycle is a bicycle with a pandemonium attachment and is > designed for the especial use of mechanical geniuses, daredevils and > lunatics." > — George Fitch, Atlanta Constitution Newspaper, 1912 > > > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
