I am very new to Arduino usage and electronics as a whole, however I do learn quickly and will be completing this project over a number of months. I am really just looking for a good starting point and any advice as far as learning resources and methods.
The Project:
I have a dual stand material tester for performing 'Elongation at Break' tests on polymers. This is a very old machine and isn't supported anymore. However, the load cell seems pretty standard and I think using a loadcell amplifier, I could send the data through an Arduino to a PC.
I am looking to plot the strain curve to a graph, so I can see MPa over time.
Is this even possible, as far as I can see it is a regular in-line strain gauge but larger, I will provide pictures.
Sorry if my lack of experience is glaringly obvious, I appreciate your time.
Even with no experience, you can get your digital voltmeter and measure and write down the voltage measured to ground of every point on your device. Once you mess with it, you will never know how it was designed to work.
Older machines sometimes used a strain gauge load cell for tension/compression and an LVDT for elongation. If you poke around you can probably find the excitation and output wires of the load cell. Measure the excitation and if you can load it up to full scale, measure and record that. Sometimes that info will be on a label or can be found from a part number. You can easily read load with a microcontroller then.
The LVDT is a little trickier but if you can probe around and find the conditioned output for that you will have little trouble scaling and reading that.
Assuming it uses lead screws to move the head up and down, you can measure the elongation accurately by measuring the rotation of the screws.
I expect the screws are run by stepper motors, as for those tensile testers a controlled and constant speed of elongation is very important. That allows for very accurate speed control. Your device may actually already have a distance signal available.
Tensile testers are actually very simple machines: a head that moves up and down, and a load cell to measure the force it takes to do so. The hard part - what makes them expensive - is in the control, and making everything stiff with low tolerance etc.
Sounds like a fun project. It's been ages since I've worked with a tensile tester, and I'd be more than happy do get to play with one again.
Look at the output of your load cell. Is it 4 or 5 wires (i.e. a strain gauge output) or is it more like an amplified load cell. Look (measure) voltages on the wires).
You also have to find the elongation output so you can read elongation (stress) and strain at the "same time".
I would try to keep the Arduino simple. Perhaps write the data to an SD card in CVS format. Then you can quickly plot the data in excel or libreoffice(free).
It has been my experience the data should be captured in its most basic form. Then apply any conversions in excel. If yo feel its better to do these conversions in the Arduino make sure you write your constants to the CVS file before starting to write data.
+1 to this.
If only so you always have access to the raw data, making it easier to re-analyse later (if you find out e.g. there's an offset to be applied somewhere or whatever).
An Arduino is also not suited to do much in the way of data analyses. It's strong point is in the data logging part.
