# Load cell for weighing powder

#### MuzMueen

Joined Dec 18, 2014
21
Hello

we are working on a project for a machine for capsule filling with powder. The powder will be filled by weight. The fill amount will be 400 , 600 & 800 mg. The error margin which is acceptable is 5 - 10 mg, so my thinking is to go with a load cell of resolution of 0.001g and total capacity of 10 - 20g. I am totally new to load cells and weighing powder side. I have done some research and I am baffled about a few things.

1. which properties of a load cell should be considered more than others in my case ? (hysteresis, resolution etc)
2. We would prefer a response time which is quicker (in milliseconds)

There are some load cells available cheaply in the market, but then there are others which are extremely expensive. Furthermore, for instrumental amplifier & ADC I am inclined towards getting one-chip solution like Texas instruments' ADS1242, so its less hassle.
If anyone of you have worked with any such situations, I would be grateful if you can share your experience and suggestion for appropriate parts.

#### GopherT

Joined Nov 23, 2012
8,012
You are trying to fill to 1 or 2% accuracy for small pills and better resolution for the bigger ones. What type of screw feeder or other mechanism do you plan do use to deposit gnats eggs to adjust your weight.

Why are you building a milligram scale when mettler-Toledo and Sartorius and many others are already very good at it? Yes, they are available with an interface.

Powders are fluffy, how do you plan to get the powder into the capsule without overflowing?

If you look at what is available in bottles at any drug store, you will see this is done all the time on what must be 100s of thousands per day scale (one machine). Why don't you look into commercially available equipment to do this - much available on the used market too.

#### MuzMueen

Joined Dec 18, 2014
21

#### cmartinez

Joined Jan 17, 2007
7,083

#### cmartinez

Joined Jan 17, 2007
7,083
Comparing a 3 bucks load cell and 900 $one .. sounds a little unfair .. ... but , i'll give it a shot .. As we say down here... "there has be something in this water for it to be holy" ... meaning that sometimes things look very ordinary in the outside but they might have very special (and secret) things in them that make them extraordinary... So it's either$3 dlls or $900.... nothing in the range of, say,$150 ?

#### MuzMueen

Joined Dec 18, 2014
21
As we say down here... "there has be something in this water for it to be holy" ... meaning that sometimes things look very ordinary in the outside but they might have very special (and secret) things in them that make them extraordinary...
So it's either $3 dlls or$900.... nothing in the range of, say, \$150 ?
well said ...
No i couldn't find something which falls under my requirement and is also around 150 - 200 .. Thats what I was actually looking for ..

#### cmartinez

Joined Jan 17, 2007
7,083
well said ...
No i couldn't find something which falls under my requirement and is also around 150 - 200 .. Thats what I was actually looking for ..
Where are you located?