I've designed ADS1230 based weigh scale. Eveything is working ok(minor glitch of ISP is solved, thanks ot Bob), display is stable.
My configuration is, Load Cell Capacity = 20kg, Excitation=ADCref=5V, PGA=64 , 10SPS. Avaraging is simple 2 sample avaraging, nothing special.
I am posting some images which display plots of internal raw adc readings and avaraged readings. These plots are created using Python+Matplotlib sampled over USB.
I would like to know how much improvement is possible(or required) through,
a) Software : Moving filter avging with more samples b) Hardware: Layout improvements. Moving to PGA=128
My aim is to get 10mg resolution with a 300gm Load Cell with the same board. As per my calculations it seems possible.
Any suggestions ? Thanks in advance.
1) Only Pan. For this Display = 0.00 kg.
2) Pan+500gm. This my Calibration Weight, Display = 0.500 kg
3) Pan+Random Weight, Display = 5.274 kg
4) Pan+Random Weight. Display = 14.040 Kg
It appears that your response is pretty good with the averaging at 2. Increasing the averaging will delay the response significantly, and depending on the type of noise may not help all that much more. I would doubt that going beyond 4 averages would be that helpful.
Increasing gain will increase the noise, but it will also increase the resolution. The measure to use is really noise free bits achieved. There should be some improvement by going to a gain of 128, even in your current load cell.
For the new load cell you should be able to get the same ratio of resolution as you are getting with the existing load cell.
I concluded the same. Unfortunately on my current board, I don't have facility to switch to gain of 128, pin is tied to GND. Although I am satisfied with current result. May be I'll spin another board, just to check the improvement in resolution :)
Thanks any way for the reply.
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