Load Cell Arrangement for Weight Measurement

Thread Starter

h.yakub

Joined Mar 11, 2019
97
Hello All,

1. I have been working on a project to measure fluid volume inside a sealed container using 200 kg Load cell sensor and HX711 Module.

2. The concept of the project is simple, that is to measure the weight of Empty container, and when the liquid is filled, we will subtract the empty container weight from the measured weight, and put it in the formula for volume of cylinder to get the volume of fluid.

3. The problem I am facing is that, I have a single load cell and I want to know how to mount it below the container, such that it gets properly calibrated and measure weight accurately.

4. The Weight of the Empty container is - 13.5 kg, Weight of fluid it can hold - 59.3 kg, Diameter of the container - 16.1 inches, Height of the container - 23.3 inches

PS: Can anyone help me with some arrangement diagram is to how to mount load cell sensor below the container. Please note, I need to make the system as portable as possible and easy to attach and detach.

Your Thoughts are more than appreciated.

Thank You..
 

mvas

Joined Jun 19, 2017
539

Thread Starter

h.yakub

Joined Mar 11, 2019
97
Are you looking for a Mechanical Design or an Electrical Design?

Small - re-purpose a small Kitchen / Food Scale using one load cell ...
https://learn.sparkfun.com/tutorials/openscale-applications-and-hookup-guide/all
If the container is not stable than add slide bearings to keep the platform level

Large - re-purpose a large Bathroom Scale using using 4 load cells ...
https://learn.sparkfun.com/tutorials/iot-industrial-scale
The 4 load cells, one in each corner, keeps the platform stable
Thanks for sharing the links, I will have a look at it.
I am looking for a mechanical design of the platform on which I can place the container.
 

kubeek

Joined Sep 20, 2005
5,794
I seriously doubt such an arrangement will work, the load cell needs to be loaded by a force that is perpendicular to it and acts upon a specific point on the cell.
Depending on where exactly the center of mass of the drum will be you will get a twisting moment in any direction on the top board - say you place the weight to the far left of the board, then you will get a negative resulting force since the cell will be bent upwards.
The top board likely has to be free floating on some pins and bushings, such that it stays perfectly parallel to the bottom and transfers the uneven load directly to the correct point on the load cell.
 

ericgibbs

Joined Jan 29, 2010
18,766
hi h.y,
I would recommend that you do not use wood or plastic in the scale Base.
The set up in post #7 is a bad idea for an industrial scale.
E

Added:
Proposed Base mounting.
AA1 03-Apr-19 16.15.gif


@h.yakub
Added suggested Spacer types:
AA1 04-Apr-19 09.09.gif
 

Attachments

Last edited:

ericgibbs

Joined Jan 29, 2010
18,766
hi h.y,
As you may know the HX711 output is a Bit stream, the data is read and converted in a MCU.
The Ardunio module has a lot of programs written for the HX711.
How do you plan to display the weight data.?

E
Attached is a marked up timing diagram.
 

Attachments

Thread Starter

h.yakub

Joined Mar 11, 2019
97
hi h.y,
As you may know the HX711 output is a Bit stream, the data is read and converted in a MCU.
The Ardunio module has a lot of programs written for the HX711.
How do you plan to display the weight data.?

E
Attached is a marked up timing diagram.
Well for this I am using Arduino Library for HX711_ADC by Olav which has a calibration program that calibrates the weighing scale with 100 g of load and then it display the weight of the empty keg. Right now I haven't tested out the program because I am focused on building the platform.
 

MisterBill2

Joined Jan 23, 2018
18,167
Several years ago I was given advice from the HBM company on a robust arrangement to do tank weighing with load cells. That setup used three bridge type cells all connected in parallel as a summing means, and it worked well, Load cells respond to off-axis loads in unpredictable and undesirable manners, so it makes a lot more sense to assure that any arrangement only puts the load force in the desired axis.
 

Thread Starter

h.yakub

Joined Mar 11, 2019
97
Hi,
Thanks for your responses.
I have used 4 load cell in bridge configuration with HX711 and it works well.
I am closing this thread now.

Thanks Again for your support. :)
 

Thread Starter

h.yakub

Joined Mar 11, 2019
97
hi h.yakub,
Thanks for the feedback, any chance you could post your final design, it may help others.:)
E
Hi E.G,

It is the same circuit that you shared containing bridge configuration. It works well with small error percentage +-1% which is not a problem. I have started a new thread, in embedded system, feel free to follow it and share your suggestion to my latest problem...;-P
 

MisterBill2

Joined Jan 23, 2018
18,167
INDEED! Ending the thread with the final design will leave a valuable resource for others to find. And since helping others is a very large portion of what this whole website is about, it makes a lot of sense to close it with the final results.
 
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