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joshua
electronics forum beginner
Joined: 07 Feb 2006
Posts: 22
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 Posted: Wed Feb 22, 2006 1:25 pm Post subject:
Urgent help need from u
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In weigh scale application can i use load cell (ranges 10kg to 100kg)
for measure below 5kg?
whether it is possible? my weigh scale application for only measure
Food products 0.1 to 100kg. |
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John Popelish
electronics forum Guru
Joined: 29 Apr 2005
Posts: 1601
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| Posted: Wed Feb 22, 2006 5:25 pm Post subject:
Re: Urgent help need from u
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joshua wrote:
| Quote: | In weigh scale application can i use load cell (ranges 10kg to 100kg)
for measure below 5kg?
whether it is possible? my weigh scale application for only measure
Food products 0.1 to 100kg.
The less of the load cell range you use, the larger noise and |
nonlinearities become, in proportion to your signal.
It gets to be a little like picking your nose with a back hoe. The
back hoe doesn't have any difficulty but its jitter and stiction tends
to leave you noseless... or faceless. |
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John Larkin
electronics forum Guru
Joined: 29 Apr 2005
Posts: 4320
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| Posted: Thu Feb 23, 2006 1:48 am Post subject:
Re: Urgent help need from u
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On 22 Feb 2006 05:25:03 -0800, "joshua" <joshuathiagaraj@yahoo.co.in>
wrote:
| Quote: | In weigh scale application can i use load cell (ranges 10kg to 100kg)
for measure below 5kg?
whether it is possible? my weigh scale application for only measure
Food products 0.1 to 100kg.
|
Good load cells are astonishing. They typically have resolution,
linearity, and stability in the parts-per-million range. A decent 100
kg load cell with good electronics will be accurate to a couple grams.
Of course, the smaller the full-scale range, the better the low-end
resolution.
Note that load cells must be zeroed ("tared") and calibrated (using a
standard weight) regularly. Their as-purchased accuracy can be as bad
as several per cent off.
This is interesting: buy, say, 25 small bags of potato chips and note
the advertised net weight. Now weigh them. You'll usually find that
none are underweight, and rarely are they more than a percent or so
over, even though a single chip may weigh several per cent of the
total. They way they accomplish this is clever and complex.
John |
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Joerg
electronics forum Guru
Joined: 05 May 2005
Posts: 3533
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| Posted: Thu Feb 23, 2006 2:08 am Post subject:
Re: Urgent help need from u
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Hello John,
| Quote: | Good load cells are astonishing. They typically have resolution,
linearity, and stability in the parts-per-million range. A decent 100
kg load cell with good electronics will be accurate to a couple grams.
Of course, the smaller the full-scale range, the better the low-end
resolution.
Note that load cells must be zeroed ("tared") and calibrated (using a
standard weight) regularly. Their as-purchased accuracy can be as bad
as several per cent off.
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That can be a problem. We bought a fancy bathroom scale a couple years
ago. It was ok for a few weeks and then showed me gaining several
weight, big time. Then losing, then gaining again. It had four load
sensors in the pods and the rest was glass plus an LCD with a uC
underneath. Nice design but I returned it. If calibrated regularly they
are great but for some applications they are more a 'technology looking
for a home'.
Regards, Joerg
http://www.analogconsultants.com |
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