scale calibration

ottoandy · Apr 23, 2009

We have twenty-five scales in the building and a few of them I have an outside source come in because we just don't have enough weights to check them.
Shipping has two large scales one is a 1500 lb. pallet scale and the other is a 500 lb. floor scale. The 500 lb. floor scale is usually being used for 50 lb. boxes and is never used to weigh anything more than 100 lbs. except the unoffical human use when anyone walking by likes to weigh themselves. Today the outside source was in for calibration and this time I was standing around and noticed that he only used up to 200 lbs. to verify the 500 lb. scale. If I know we only use this scale for 50 lb. boxes then it seems that I should be able to use a 65 lb weight to verify this scale.

Many scales are used for specific operations, so would it be acceptable to use the matching weight to verify the scale?

Andrew

The real Leigh · Apr 23, 2009

ottoandy said:
Many scales are used for specific operations, so would it be acceptable to use the matching weight to verify the scale?

Hi Andrew,

If depends on what you mean by "calibration".

If you're talking about a service that comes in, checks the equipment, and puts a sticker on it saying that it meets manufacturer's specs, then the tests will be done according to the manufacturer's instructions.

The calibration company doesn't know or care what you use the scale for.

The same is true for calibration of any other piece of equipment.

In many industries and applications, accurate measurement of weight is mandated by law. This is what the calibration company is concerned with. For all they know, you might use that scale for soy beans tomorrow, and it better be right.

If the scale bears a manufacturer's label that says "Not legal for trade.", then there's a bit more flexibility. This usually means that the scale is not accurate enough to meet legal requirements.

- Leigh

rkward · Apr 23, 2009

I believe they are just checking to see if it is linear up to a certain point. Beyond that it probably doesn't matter up to the max. Also, the larger the max weight the less the granularity of the scale. A scale capable of weighing 500 tons might not be able to weigh the average person any more accurately than +/- 100 lbs. or so. A single weight alone would not be used to calibrate them but rather a series of them.

ottoandy said:
We have twenty-five scales in the building and a few of them I have an outside source come in because we just don't have enough weights to check them.
Shipping has two large scales one is a 1500 lb. pallet scale and the other is a 500 lb. floor scale. The 500 lb. floor scale is usually being used for 50 lb. boxes and is never used to weigh anything more than 100 lbs. except the unoffical human use when anyone walking by likes to weigh themselves. Today the outside source was in for calibration and this time I was standing around and noticed that he only used up to 200 lbs. to verify the 500 lb. scale. If I know we only use this scale for 50 lb. boxes then it seems that I should be able to use a 65 lb weight to verify this scale.

Many scales are used for specific operations, so would it be acceptable to use the matching weight to verify the scale?

Andrew

ottoandy · Apr 23, 2009

If a scale dosen't verify in specification then I go through the calibration process that the scale manufacturer will run me through.

howiesatwork · Apr 23, 2009

If the 500 lb floor scale is one that uses slotted add-on weights put on the end of the scale beam, then the biggest of those add-ons should add 100 or 200 lbs to the reading of the scale.
200 should be enough if it's that style scale.
If the the scale reads from 0 to 500 lbs contiguously, 500 lbs of weights would be needed to cover that scale range.
Another thing a few don't check is the platform repeatability. It should read exactly the same when the mass is put nears the corners of the platform as it does when the mass is in the middle of the platform.

ottoandy · Apr 24, 2009

platform repeatability

The 500 lb. scale is a digital Cardinal floor scale without a balance beam. I like that thought of checking the platform repeatability, I will check that today to satisfy our confidence.

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