Can someone explain to me how this (as advertised) full bridge load cell works?

enter image description here

I'm aiming for good temperature stability and I understood a full bridge load cell configuration should reject error from temperature variation based on the fact that you're measuring the difference between two elements.

This particular load cell varies by about 1% per 1°C.

I'm struggling to see how this configuration is an improvement over a single, 2-wire resistive element at all.

  • \$\begingroup\$ allaboutcircuits.com/textbook/direct-current/chpt-9/… \$\endgroup\$ – Bence Kaulics Sep 27 '17 at 8:47
  • \$\begingroup\$ What does the data sheet say? If it doesn't have a data sheet why would you consider using it and why would anyone bother to take a guess? \$\endgroup\$ – Andy aka Sep 27 '17 at 11:44
  • \$\begingroup\$ Thanks for the link Bence. This confirms my understanding of load cells and that there should be a positive and negative element (you essentially measure the difference). Whereas this unit only measures positive force (the resistive elements are both on the same side) I've also seen this link which goes into a little more details on the maths omega.com/toc_asp/… \$\endgroup\$ – Wilson Waters Sep 28 '17 at 1:29
  • \$\begingroup\$ Andy, the spec sheet indicates a temperature accuracy of 0.1%F.S/10°C whereas I'm measuring about 100 times higher than that. imgur.com/a/8Yf9r \$\endgroup\$ – Wilson Waters Sep 28 '17 at 1:32

Let suppose you have this kind of gauge:

enter image description here

This is a half leg of the Wheatstone bridge, it has two gauges positioned 90 degrees apart with respect to each other. One gauge measures the elongation due to applied force, while the other doesn't change the resistance.

Because of thermal elongation, both gauges elongate in both directions, so the second gauge is there for this temperature compensation.

Very good cells are built with materials, body and gauge, with similar/equal temperature elongation coefficient, this further makes a load cell temperature stable.

Don't expect from cheap cell, like in the picture, some very accuracy and stability, it's not just about to glue the gauge on piece of metal.

  • \$\begingroup\$ This is really interesting. I didn't realize there are two elements per sensor. What would be the advantage of using two sets of these dual elements - both measuring positive force as per the sensor in this image \$\endgroup\$ – Wilson Waters Sep 28 '17 at 1:38
  • 1
    \$\begingroup\$ @WilsonWaters Two sets form the full Wheatstone bridge. Yours have probably a set with two gauges oriented in the same direction, thus more sensitivity to the force, and unfortunately sensitivity to temperature. \$\endgroup\$ – Marko Buršič Sep 28 '17 at 8:45

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