analytical balance

Factual Questions
1

Hello everyone,

So this is my first post, and I’m sure some may get mad at me for asking a homework related question, and for that I am sorry. But I really am stumped. I have searched my textbooks, the internet, the encyclopedia to no avail.

Yesterday I learned how to use an analytical balance in Science class. As part of my homework we have to answer all sorts of questions and do all sorts of conversions. When I asked my teacher this very same question (that I didn’t know was going to be part of my homework BTW) he told me I would have to find out for myself, well I have tried that and I can’t find anything, here is the question:

“What is the detection limit or lowest possible reading on a standard laboratory analytic balance? Express this in grams and milligrams”

I know how to convert units, but how on earth do I find what the detection limit is? Does anyone know? Thank you in advance.

Patiently weighting…(joke)

2

Here’s your required reading:

http://www.dnr.state.wi.us/org/es/science/lc/OUTREACH/-Publications/LOD%20Guidance%20Document.pdf

That’s as much help as I’m going to give you. Good luck!

3

Thank you! So very fast too, WOW! I like this place, I’ll try to contribute if I can (in between mounds of homework that is!) Cheers!

4

33 pages? Yipes.

Calculating the actual detection limit of a measurement device is a statistical exercise, and can get mathematically intensive. It also involves understanding advanced concepts such as noise, quantization, SNR, etc.

Is the OP certain that that’s what the teacher is looking for? Maybe the teacher is just looking for the resolution (a.k.a. readability) of the readout.

A standard analytical balance (e.g. one made by Mettler) usually has a readability of 0.1 mg. Could this be the answer the teacher is looking for? 0.1 mg is also the “lowest possible reading” for a standard analytical balance. Of course, this doesn’t mean the uncertainty is 0.1 mg…