weigh scale design

[bhaskarm]

Hi all,
I want to design a weigh scale with 1mg(milli gram) resolution and range will be 600 g to 1mg.I am new to this weigh scales.I want to design this weigh scale for the low cost as well.This is for jewellary shop.
kindly let me know the ADC and micro controller that I have to choose.If possible provide me the design circuits.

Thanks in advance.

Thanks,
Bhaskar

 

[KMoffett]

600,000 mg range You would need a 20 bit ADC. I don't think it's going to happen.

Ken

 

[blueroomelectronics]

Why not just buy a scale? How would you certify calibration?

 

[DSGarcia]

You are asking for too much from a scale. If you have to build the scale yourself, you should build two scales; one for up to 600 grams that could easily weigh to the nearest tenth gram and a smaller scale (perhaps 10 grams max) to weigh to the nearest milligram.

If the scale is being used to sell something based solely on its weight, then you have the problem of certifying the scale. If you simply want to use the scale in your process or get a rough idea of material in order to consider when determining an asking price, then you should be fine as long as there are other factors used in considering the price, such as design, labor, etc. but it seems to me that if that is the case you wouldn't need such accuracy. Why is weight to the nearest milligram important?
Dale

 

[Mr RB]

Anyone can get a 500g 0.1g scale cheap on ebay. I use one here for counting 100's of components, many of them have a count function.

As for a 1mg scale for jewellery, they can already buy many types of certified scales for measuring gems etc, they may not be "cheap" but then there aren't many POOR JEWELLERS. Trying to design a budget device for jewellers just seems dumb.