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I know that a bar type load cell needs to be setup as shown here as to flex the strain gauge enter image description here

However, most tutorials or guides show how to setup an S type load cell like this (for tension)enter image description here

and not much info on how to setup for compression. Im guessing the load does not need to be right on top of the screw hole as per the bar type? I would be able to mount a platform directly onto the top and bottom surface of the "S", right?

On another note do most load cells already come wired with a wheatstone bridge? (some dude in a tutorial mentioned this)

I'm a newbie and I'd appreciate any advice.

Edit: This is the load cell Im looking to purchase. Does not mention much other than the material properties in their 'datasheet'. link

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Your ability to calibrate a load cell is going to depend on the orientation of the strain gauges inside the load cell, which is determined by however the manufacturer chooses to apply or embed them.

There are all kinds of "tricks" you can do with strain gauges, like being able to remove the effects of bending moments, thermal compensation, etc., but again it all depends on how the strain gauges are applied.

If you are at all unsure of how the load cell is intended to be used then the first place you should go to is the datasheet.

The top image in your question looks like it's setup to torque the load cell, but if you have a strain gauge on top and one on bottom, and they're wired in series, then one strain gauge is in tension when the other is in compression and the net result is (nearly) zero change in total resistance - this is one of the "neat tricks" I mentioned previously. Such an arrangement would give (virtually) no change in reading if you were to put that on a countertop and place items on it like a weighing scale, but WOULD give you a change if you were to mount it on a wall and use it like a coat rack.

Again, it all depends on how the strain gauges are installed and wired. Consult the datasheet!

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  • $\begingroup$ I appreciate the feedback Chuck. Ive been looking for extra info on the products but the most I can get is the material properties from their 'datasheet' (link added to original post). Is there like a 'default' method of setting up a certain type of load cell? ie for an s-type, you wouldnt need a force directly applied at the position of the screw holes (assuming just using for a normal setup - load cell on the bottom, load on top) $\endgroup$
    – C. Wagner
    Jul 1 '20 at 2:59
  • $\begingroup$ @C.Wagner - In looking at your link, I think the most generic advice I could give is that you should load it along (colinear with) the bolt holes, such that you could string it up as an in-line force sensor, like the bottom picture in your post. It looks like they're using a standard wire color code for the load cell, so you could hook it up to a load cell driver like this one (not endorsing that product, just the first one I found online.) $\endgroup$
    – Chuck
    Jul 1 '20 at 17:37

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