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I am looking for a scale to use for a project. I have scoured and found some options that are mostly for weighing humans and small items as well as some fully integrated systems for inventory management (Which are too expensive).

The items that I need to weigh are approximately 4 feet long. We need to be able to measure up to 40 lbs. at a minimum. Accuracy is not that important, being off by up to 1 lb will not affect this particular project

The plan is to integrate these scales into a shelving systems and have them monitor the weight of the product in each location. We will need to take the measurements from the scale and pass that back into our internal application.

We would consider using load sensors and effectively building our own platform but first want to reach out and see if anyone has seen such an animal.

The secondary option would be to use multiple scales at each end of the shelve using the method show Here. Who knew I would every use the Physics SE.

Lastly if a long scale is not an option and we have to move to the method show on Physics SE then we would like the scales to be as small as possible.

  • "monitor the weight of the product in each location" by location, you mean the shelf itself correct? – BigElittles Jan 23 '17 at 17:51
  • I like the idea, but I have a feeling your are going to be hacking a "wifi scale" to meet your form factor... OR using FSRs/load cells attached to a raspberry pi or arduino to accomplish it. If your doing what I think you are doing... I'd consider buying rfid tags in bulk for each box, and a passive scanner for each set of shelves. Program the tags with the inv details (weight, name, etc etc) and assign it to a specific scanner. If the scanner looses contact with the rfid tag, then notify the person who needs to know that information. Depends on how much inventory your going through though. – BigElittles Jan 23 '17 at 18:07
  • @BigElittles I do mean the shelf itself. RFID will not work we already have this technology. We have boxes of glass tubes. There are anywhere between 50 and 100 tubes in each box. So it would be very difficult to tag each one. On a side note. I am already going to the fact that I will have to go the FSRs/load cells method. – Jeff Jan 23 '17 at 18:09
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I hope I understood correctly: You're asking for a computer connected scales that can weigh tube-like items about 1.2 m long and ~20 kg in weight, and that does not cost a fortune.

A so-called "smart" bathroom scales would meet these requirements, when applying the following modifications:

  1. Choose scales with a known interface. Smart bathroom scales have a Bluetooth 4.0 and / or wifi connection. Since you want to connect it to your internal software application and don't want to make that dependent on any cloud hosted "solution" by the scales' manufacturer, you would choose one where the protocol has already been reverse engineered and some code is available for the Bluetooth communications.

    For that, have a look at the supported scales in openScale and the code to support them. These are all Bluetooth scales, so you'll need a Bluetooth 4.0 endpoint in your network, for example a Raspberry Pi 3. (Anything that only supports Bluetooth 3.0 is not compatible.)

    It would be nicer to use a wifi scale, to avoid the Bluetooth device in your network and the need for developing the Bluetooth communications software. However, hacking the wifi scale to connect to your own server rather than the manufacturer's server involves bending the DNS (example for the Nokia / Withings Body), which you could consider an ugly hack that you don't want.

  2. Enlarge the scales' platform. A typical smart scales consists of four load cells and an electronics board, all connected with wires (example). I think that there will be no change in the scales' function or accuracy when you extend these wires and then mount the load cells and electronics into a larger, 1.2 m long platform that you build yourself. (However, since I did not try this yet, you'll have to try first …)

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