1 Gram scale

Other Hardware Motors, Mechanics, Power and CNC
1

Hi,

I have a scale from China that weighs paper. The sensor (please see attached) has four lines connected to it. That connect to a board, and I think it says this:

E Black Wire
S+ Green Wire
S- White Wire
E+ Red Wire

I am thinking that the E is negative, and the E+ is positive. And the other two are for getting the sensor response. But when I try to read the values I get the same readings. Nothing changes even though when I press down the weight changes.

Does anyone have any ideas?

Thanks,

Cameron.

2014-01-23 16.05.29.jpg
2014-01-23 16.05.29.jpg2560×1920 1.03 MB

2

That is a load cell, it changes the resistance only slightly.

A load cell is a good sensor. It can be very accurate. But a amplifier is always needed.

You will find lots of information about load cells and Arduino.

http://cerulean.dk/words/?page_id=42

3

Thank you!

That page looks great! Even the connections seem the same. So the reason i didnt see anything on my multimeter is because the signal was just too low for it to read?

Thanks cam

4

cameronasmith:
So the reason i didnt see anything on my multimeter is because the signal was just too low for it to read?

You typically need to amplify the signal around 500 to 2000x. Too little amplification ("gain") and the signal, the difference in voltage between the S- and S+ lines, will sit at zero and too much and it will sit at ~3V. Load cells are very finicky about getting the right amount of amplification.

5

The change in resistance was too minimal to measure.

A load cell is actually a piece of aluminum with two strain gauges glued to it.
By making the aluminum a certain shape, the change in resistance is linear to the distortion of the aluminum.

More than half of the digital bathroom scales have a load cell. Some have just one, others have four. they can be bought at garage sales very cheap sometimes, because the battery is empty. It's fun to see what is inside.

6

Do you think because my Load Cell is designed for paper it requires more amplification than for something like a bathroom scale?

Thanks,

Cameron

7

Doubtful. The strain gauges on the load cell are pretty standard; it's the configuration of the aluminum bar they are glued to that allows it to flex more under lighter load.

8

Caltoa:
The change in resistance was too minimal to measure.
A load cell is actually a piece of aluminum with two strain gauges glued to it.
By making the aluminum a certain shape, the change in resistance is linear to the distortion of the aluminum.
More than half of the digital bathroom scales have a load cell. Some have just one, others have four. they can be bought at garage sales very cheap sometimes, because the battery is empty. It's fun to see what is inside.

Me totally agree with the statements and references. It's right and correct information about scales and load cells with references.