Scales and Accuracy - Getting scale companies to give out accuracy for their scales

[fortyfour73]

Good day to all,
Currently took position at company as calibrations tech. In doing so finding scale procedures wacky and trying to straighten out. biggest issue is getting scale companies to give out accuracy for their scales. found in NIST handbook graphs, etc., but find myself getting lost.
Can anyone help in stepping me through this. Lets say scale is 3100g max. what is the accuracy and what standards are resonable to use for calibrations?
Thanks to anyone who may be able to help me.

 

[crendfrey]

Re: Scales and accuracy

Greetings Forty.

The accuracy or resolution of a scale is stated in the manufacturer’s sales literature.
You should also be able to find it in the user’s manual of the scale.
Each scale has different specifications and will be used for different purposes.
Looking up the make and model number at the manufacturer’s web site should give you the info you need.

Handbook 44 is a good place to start. Remember H-44 is the “book” for legal for trade issues.

Our policy is to use class 1 weights for anything 10,000 divisions or more.

If you need help with your calibrations, just let me know.
To be fair I must state we are a calibration lab

 

[BradM]

Re: Scales and Accuracy - Getting scale companies to give out accuracy for their scal

Crenfrey is right. Handbook 44 is the standard for such items.

I would recommend you searching the site on internal calibration threads. More specifically, I know there are threads dealing with internal calibration of scales.

Outside of Handbook 44, the determination of the tolerance is a compilation of several factors, including the mfg. tolerance, environment, vibration, etc.

Say we have two identical model XYZ scales. One of which is in a sterile area, and all weight is lowered by crane. A high class of weights are used for calibration. The other is in a grain mill, and the weight is rolled on with a cart (a heavy cart). A lower class of weights are used for calibration. Same scale, but will need to have different assessments.

Another method is simply to determine what accuracy you need the scales to be at, and calibrate to that.

Aside from the accuracy, you will need to determine what test points you want to verify.

I would start by searching threads by Hershal Brewer and Wesley Richardson on this site in addressing uncertainty, the calculation, and the different environments.