limitations of accuracy in electronic scale
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MUEE Discussion Board :: Electrical Engineering Subjects :: ELEN30013 Electronic System Implementation
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limitations of accuracy in electronic scale
in one of the lectures when we were doing the exam Q example where we have a mass and a spring and we have to create a electronic scale to measure the mass.
one question is "discuss the limitations of the accuracy"
what exactly would we say for this? all i can think of is that the arduino has the accuracy of (1/1024)*5 for its analog inputs
i think though there might be some other things i am missing, any thoughts guys?
one question is "discuss the limitations of the accuracy"
what exactly would we say for this? all i can think of is that the arduino has the accuracy of (1/1024)*5 for its analog inputs
i think though there might be some other things i am missing, any thoughts guys?
Lev- Posts : 4
Join date : 2010-11-20
Re: limitations of accuracy in electronic scale
I didn't do ESI but I would say generally two major limiations would be your sampling rate (and processing time of a sample) and the systems noise performance.
Cheers,
Bryce
Cheers,
Bryce
BBNT- Posts : 2
Join date : 2010-11-20
Re: limitations of accuracy in electronic scale
What do you mean by system noise performance?
koya_smak88- Posts : 1
Join date : 2010-11-21
Age : 33
Location : Brunswick
Re: limitations of accuracy in electronic scale
In regards to 'noise performance', refer to the equation given by Peter, which is the Johnson-Nyquist Noise equation (look it up on wiki).
The 4 things identified by Peter were:
- Resolution of A2D conversion. we have to measure mass up to 1kg, so 1kg/(1024 quantisation levels) ~= 1g accuracy.
- The noise voltage as mentioned above
- The spring has no (explicit) damping. Therefore it will oscillate for some time after a mass has been placed on the contraption.
- In calculating the mass, we assume gravitational acceleration to be constant (ie. 9.8m/s^2) when it is actually location-dependent
One other thing is the tolerance and non-linearity of the slider pot. This will affect the voltage reading probably alot more than any of the other stuff.
The 4 things identified by Peter were:
- Resolution of A2D conversion. we have to measure mass up to 1kg, so 1kg/(1024 quantisation levels) ~= 1g accuracy.
- The noise voltage as mentioned above
- The spring has no (explicit) damping. Therefore it will oscillate for some time after a mass has been placed on the contraption.
- In calculating the mass, we assume gravitational acceleration to be constant (ie. 9.8m/s^2) when it is actually location-dependent
One other thing is the tolerance and non-linearity of the slider pot. This will affect the voltage reading probably alot more than any of the other stuff.
lewy78- Posts : 1
Join date : 2010-11-21
MUEE Discussion Board :: Electrical Engineering Subjects :: ELEN30013 Electronic System Implementation
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