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Subject: Re: Eliminating Ground Vibrations in a electronic weighing scale

Date: 07/25/03 at 8:56 AM
Posted by: Pieter Hoeben
E-mail: pieter@hoeben.com
Message Posted:

In Reply to: Eliminating Ground Vibrations in a electronic weighing scale posted by Prashanth.T.G on 07/16/03 at 7:41 AM:

Hi, I developed electronics, hardware and software for dosing systems myself. Vibrations depend on your machinery. A machine is always a mass-spring construction when you are weighing. Some typical machine frequencys are 10 to 25 Hz.
The relation of stifness of the frame and scale determines what comes into your scale. What you can do is filter this. You can use an averaging filter (take the average of all measurements of the last second as output), you can also do FIR filtering etc. But take care: when you have a higher input frequency (for example a machine vibration of 16 Hz) that is larger than your samplng frequency/2 (example 30 meas/second / 2 = 15), you get aliasing (in this case 16-15 = a 1 Hz signal) that CANNOT be filtered. That is why I made weighing/dosing systems that did a couple of hundred measurements a second, and then filtering. This does give some demands to your hardware. You can also use a analog anti-aliasing filter. There comes more to it, too much to describe here. If you want more info, feel free to contact me at email: pieter@hoeben.com

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