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In this Discussion
- brnyza March 2014
- processor65 February 2014
Weight Scale Part 1 (High A/D Resolution and GUI)
Hi all: This is a High Resolution Weight Scale GUI built with Arduino UNO and Processing 1.5.1. I have been playing with high resolution before in some of my previous projects; but nothing like this. Using the same 10 bits A/D converter from Arduino which will normally resolve 1024 different voltage values in the 0-5V interval, the system is resolving almost 100000 different voltage values in that interval (in the grams scale), which corresponds to about 5/100000= 5 microvolts voltage steps. The result is quite stable as the video shows. Neither amplification nor hardware noise reduction techniques are in use. The pot is directly connected to the Arduino A0 input. In the other scales (units) the resolution is even greater (shown by the end of the video). To achieve this resolution, of course, the overall frequency response of the system had to be drastically reduced and the total response time is slow. In general, it has to be a very slow moving variable to tolerate this. I tried to add some dithering; but there was no noticeable effect, either because I was doing it wrong or because there is already enough noise present in the signal. I don't have a clear answer on that yet. As in previous projects all the data collected while the Graph is running is logged directly into Excel (shown at the end) I'm currently working on a real version using a real weight (bridge) sensor and an instrumentation amplifier. Still making final adjustments. The performance is nowhere near this one and I had to reduced the resolution by one order of magnitude to obtain some acceptable results. I used this project to improve the Gauges GUI I had already built and the Graph which will be very useful in many future projects. Arduino and Processing are really awesome.
Comments
Let me emphasize that noise is a big problem and for this to work properly it has to be kept under control at the right level. Too much noise and there will be instability and errors. The drastic reduction of the frequency response helps reducing noise; but on the other hand reduces the response time. Its a delicate trade off.
One more thing: since I don't have the instrumentation required, I have not performed any serious accuracy, linearity or repeatability tests and for that reason the preliminary tests I have performed in these areas are inconclusive.
How did you get Hi resolution with Arduino UNO hardware(10bits)?
Thank you.