Load Cell has abnormal wire coloring

Question

pulled a load cell from a small scale that I bought from amazon. I read online about how to use a INA125P to amplify the signal from the load cell, but when i examined the load cell i pulled from the scale, I found the wire coloring did not match that of the tutorials I read. I even found some lists that show wiring colors by manufacturer and all of them seem to at least have a green wire, whereas my wires are red, white, yellow and blue. Here is a picture of my load cell. I've tried Googling the text on the cell as seen in this picture, with no luck.

Perhaps an understanding of how a load cell works on a more fundamental level could allow me to reverse engineer the wiring with a multimeter. Or is there some other way of determining the wiring of this load cell?

Answer 1

All a load cell is, is a collection of resistors that change resistance when they are flexed (flex sensors).

You get different numbers of flex sensors in different models. The most common is 2 sensors, which it looks like yours are. That's two wires per sensor.

It looks easy enough to work out which wires connect to which sensor - you just need to experiment to work out which way round those wires connect.

You use it as part of a Wheatstone Bridge - that is, along with two more resistors:

So one wire from the compression (or "top") load cell goes to the positive of the excitation supply, and one wire from the tension (or "bottom") load cell goes to the negative (or ground) of the excitation supply. The other two wires join together and form the middle node of that branch - the "positive" output of the bridge. The "negative" output is the mid point of your two reference resistors, and it's the difference between these two voltages that you are interested in.

Your job now is to work out which way around the two wires from each sensor go. Don't be afraid to experiment.

If you get it right it will work. If you get it wrong one of these will happen:

1. Your readings will be backwards (you have both pairs of wires backwards)
2. You won't get any readings (or hardly any) - you have one pair correct and the other pair backwards.