Where to purchase low-cost load cells??

[sbsmotorsports]

Hi,

I'm working on a product for my business. I am trying to compete with other companies that make weigh scales for cars. The systems consist of 4 scale pads. Each pad will need to measure a max weight of 1500 lbs.

I have found several load cells that will work, but they are too expensive. The cheapest I've seen is around $125. I am looking for a load cell in the range of $50 that will meausre the weight. It doesn't need to be super accurate +/- 2 lbs is fine.

I've tried making my own but the measurements aren't repeatable.

Anybody know of a source for low-cost load cells?

Thanks,
Sal

 

[MikeHalloran]

- Ask for OEM components, e.g. from these guys:

http://www.scaime.com/USweb/whoweare.html

- Ask your strain gage supplier to help you get your design and assembly process under control. The strain webs need tight dimensional control, at least within a cell. You need overload protection in some form, e.g., the strain under the gages must be limited. The gages must be installed perfectly, and protected from moisture.



Mike Halloran
Pembroke Pines, FL, USA

 

[Ashereng]

Hi Sal,

+/- 2 lbs on a 2000 lb car is 0.1%.
On a 4000 lb car, it is 0.05%.

I am not familiar with strain guages/load cells, but in the instrument world, 0.05% of full scale is pretty accurate, and comes for more than $125 for a flow element.

Or, did you mean a resolution of +/- 2 lbs. That would be different.

 

[MintJulep]

My bathroom scale obvioulsy uses some cheap load cell.

 

[Metrics]

First I recommend the "The Tale of the Scale" by Solly Angel for anyone silly enough to design a load cell (a bathroom scale in the book) without any experience.

If that doesn't convince you, I might have a proposal.

The idea involves using a small sputtered thin film cantilevered beam with a full 5000 Ohm whetstone bridge. The price should be less than 4 individual strain gages in larger quantities.

This small beam could then be attached to your steel load cell element without adhesives in about 30 seconds.

Repeatability, hysteresis and long term stability should be better than .1% full scale, but will depend on your element, loading condition and environment. Outside of a controlled environment, a 1% accuracy would probably be more realistic for the system.

I could provide samples immediately, but production quantities would be about 2 months out.

 

[sbsmotorsports]

Hi Metrics,

Can you send me some technical information/prices about the gages you are talking about?

You can send them to: sal@sbsmotorsports.com

Thanks,
Sal

PS: I've located that book at the public library. I'm going to swing by and check it out. Thanks!

 

[DAVIDSTECKER]

Have you looked into using short stroke hydraulic cylinders with a 1 sq. in. area (1.128" dia.) and a 0-3000 pound per sq. in. gage or what ever range of gage that would put your weight in the gage's mid range.
You could do variations of the area to work with any pivot pins or other stablizing methods you may need.

 

[btrueblood]

Measurement specialties,

http://www.meas-spec.com,

manufactures fairly low-cost ($15-20?) MEMS load cells in 50 to 2000 lbs range. You can buy the bonded elements (in 10^6) quantities) for a couple bucks each. These are glass frit bonded strain gages, which reduce problems with epoxy creep and scale drift over time.