Build a Thin, Durable Scale for Rough Terrain: Force Sensor Options

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Discussion Overview

The discussion revolves around the challenge of building a thin, durable scale suitable for rough terrain, with a maximum thickness of 8mm and a load capacity not exceeding 10kg. Participants explore various force sensor options, considering their specifications, costs, and practical applications.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses the need for a thin scale and discusses the limitations of various force sensors, including load cells, strain gauges, and force sensing resistors, citing concerns about cost and accuracy.
  • Another participant suggests a specific subminiature compression load cell that meets the thickness requirement but notes the high cost of purchasing multiple units for scale production.
  • A participant questions how commercial bathroom scales can be produced at such a low price, indicating a desire to understand the manufacturing process or materials used.
  • One participant proposes a hands-on approach, suggesting that reverse engineering a low-cost bathroom scale could provide insights into building a similar device economically.

Areas of Agreement / Disagreement

Participants generally agree on the challenges of finding suitable sensors that meet the specified requirements, but there is no consensus on the best approach or solution to achieve the desired scale design.

Contextual Notes

Participants express concerns about the accuracy and cost of various sensor options, highlighting the need for a balance between performance and affordability. There are unresolved questions regarding the manufacturing techniques used in commercial scales.

Who May Find This Useful

This discussion may be useful for individuals interested in sensor technology, scale design, and cost-effective engineering solutions in the context of building measurement devices for specific applications.

refind
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My task is: I need to build a very thin scale (like a bathroom scale), less than 8mm in thickness total, and needs to work even if placed on rough terrain (so it needs it's own bottom and top). The total load will not exceed 10kg.

I've been trying to look for the correct force sensors to use but I haven't found anything too attractive. Load cells are large and expensive, strain gauges look promising but I'm afraid of bridge balancing issues, and force sensing resistors are garbage because of drift. I need accuracy of +/- 5% or better, so does anyone know any sensors I could try?

Thanks!
 
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Here's some Subminiature and Miniature Compression Load Cells.

According to the Specs, the 20 kg capacity http://www.omega.com/pptst/LCPB.html is only 4 mm thick. Here's a dimensions picture from their specifications PDF file.

attachment.php?attachmentid=61440&stc=1&d=1378278830.jpg
 

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This is a good product but buying 4 for a scale would be $480. I need to make several of these scales so the cost adds up too fast.

How do they make bathroom scales for $15?
 
refind said:
This is a good product but buying 4 for a scale would be $480. I need to make several of these scales so the cost adds up too fast.

Ah. You did say ±5% and be 8 mm thick.

How do they make bathroom scales for $15?

I don't know. Maybe that would be a good place for a little hands-on.
 
dlgoff said:
Ah. You did say ±5% and be 8 mm thick.

I don't know. Maybe that would be a good place for a little hands-on.


for a $15 investment to strip one and do some reverse engineering would be $15 well spent in my book

Dave
 

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