Three wire strain gauge.

[Timmmm]

Hi, I've dismantled some bathroom scales to use the load cells in another project, and I want to convert the weight to a voltage. There are several tutorials online for this, but they all use strain gauges with four wires. Mine have three (red, black, white). I measured the resistance between them and it is (as far as I remember):

White->Red: 1k
Red->Black: 1k
White->Black: 2k
White+Black->Red: 0.5k

Which to me suggests some kind of white-red-black voltage divider.

Any idea how this is all connected? There is only one strain gauge on one side of the load cell cantilever.

Cheers.

 

[ericgibbs]

Hi, I've dismantled some bathroom scales to use the load cells in another project, and I want to convert the weight to a voltage. There are several tutorials online for this, but they all use strain gauges with four wires. Mine have three (red, black, white). I measured the resistance between them and it is (as far as I remember):

White->Red: 1k
Red->Black: 1k
White->Black: 2k
White+Black->Red: 0.5k

Which to me suggests some kind of white-red-black voltage divider.

Any idea how this is all connected? There is only one strain gauge on one side of the load cell cantilever.

Cheers.

hi,
From your description you have a 'half bridge', the other arms of the bridge are most likely fixed 1K precision resistors.
Can you say what voltage was across the White/Black ends, it looks as thought the output is Red.
Are you able to see the fine wire load cell elements and how they are mounted.
Its important to know if the element pair are in compression or tension

EDIT:
Look at the image, I would consider the left hand option as being the correct one.

 

[Reloadron]

You could give this a read. They discuss 2 and 3 wire quarter bridge circuits. That may help you understand what you have.

Ron