Multi-touch Scale?

September 7, 2014 5:52 PM

Is there such thing as a scale that can weigh multiple items at once (as in, display their individual weights)?

I'm imagining a pad with 3-4 separate items on it. This scale would have some sort of display showing the footprint and weight of each item. Anything like this out there?

If I wanted to build something along these lines, could I use the same tech used for touchpads? I know they're pressure sensitive already (i seem to remember a heat map on an old computer showing how hard you were pressing).

posted by stinkfoot to Technology (7 answers total)

computer touchpads do the heatmap thing through capacitance. scales work with a load cell.

there are scales like this, but they simply have more than once load cell+surface to weigh things on, so you're not actually putting each item on the same plate to be weighed. You'd end up with something like a grocery store meat counter double scale, or bigger. Or something that can weigh more than one hanging item at a time...
posted by emptythought at 6:00 PM on September 7, 2014

Best answer: You don't want to use touchpad technology, since it doesn't work the way you think it does. It's measuring the presence of a finger using capacitive sensing much like the screen of a smartphone does. There's an array of electrical sensors and it finds the center of your meat-finger coming electrically close to the glass. The size of the finger can be used to simulate the reading of pressure (imagine a pinky tip showing as a tiny circle, and pressing your pinky really hard as a larger circle).

You'll probably want to look at the technology used for sensing actual pressure, like this system used by orthopedists and the like. This stuff can sense multiple gradients of pressure, but I fear the resolution won't be good enough to weigh typical things you would weigh on a scale.
posted by JoeZydeco at 6:02 PM on September 7, 2014

Are you more interested in the weighing or in the displaying?

You could make something that appeared to be doing this, if you knew the weight and objects in advance. Using a vision type multitouch table (eg MS PixelSense) you could create a program that identified the objects and displayed their weight and footprint information that had previously been loaded into a database.
posted by keeo at 7:11 PM on September 7, 2014

You might be able to use one of those foot pressure thingies to do this.

You couldn't do it out of the box, but it'd be pretty straightforward to write software that would detect the individual items and display their weights.
posted by Hatashran at 7:42 PM on September 7, 2014

Best answer: You could build an array of force-sensing resistors; for example these from Sparkfun, connected to a microcontroller such as an Arduino. These sensors can respond to variable levels of force, and a grid of these could be used to measure where force is being applied across a larger surface.

There's a startup called Tactonic working on creating larger surfaces that can measure variable pressure, based on prior research from NYU. However, the development kits are quite expensive, so depending on your needs you might be able to make your own for less.
posted by shaun at 11:41 PM on September 7, 2014

If you have a scale that supports tare reset (mostly used for subtracting the weight of a container) you can add items one by one, taking note of the weight of each, then press the gross reset button to get the total. Lots of cheap digital kitchen scales can do this.
posted by monospace at 9:58 AM on September 8, 2014

Response by poster: Thanks folks- sounds like for my application (very accurate weights) I might be better off using multiple scales. Thanks again or the input though!
posted by stinkfoot at 7:05 PM on September 8, 2014