Load cells

[Jack Gifford]

I'm not sure which forum is the most appropriate for this topic?

I want to use an S-type load sensor (in tension), but am not familiar with them.

> Is the load intended to be applied to the U-shaped openings, with the tapped holes to be used for load-link retaining bolts?

> Is packaged circuitry readily available to provide an analog output of 0-5 volts DC that is directly proportional to the applied force?

Thanks

 

[Compositepro]

You can do it that way but no. The load is intended to be applied through the bolts in those holes.

https://www.hbm.com/en/6768/what-is-a-load-cell-and-how-does-a-load-cell-work/

https://www.omega.com/prodinfo/loadcells.html

Follow the links on the Omega site for tutorials. You have a lot to learn.

 

[RodRico]

Read Compositepro's links and remember applications engineers are your friend.

 

[Jack Gifford]

To clarify- I'm retired from an EE career, including work with strain gauges. What I "... have a lot to learn..." about is the typical load cells on the market, such as S-type configuration.
> Do they typically contain a Wheatstone bridge, or merely the piezo strain gauge?
> To obtain an analog 0-5 VDC output, are there pre-engineered circuits available for purchase?
Thanks

 

[GregLocock]

They use a full bridge, that's why they have 4 wires.

Strain gage amps are readily available in all sorts of forms and prices. Hobbyist ones are as little as $7, proper ones can be $1000 (or more, no doubt)

https://circuitdigest.com/microcontroller-projects/arduino-weight-measurement-using-load-cell

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[Jack Gifford]

Thanks Greg

 

[Compositepro]

Gosh, if you had even glanced at the links I gave you, you would have immediately seen what Greg just told you.

 

[Jack Gifford]

I'm looking at using a PSD-S1 S-type load cell (from Walfront, 350 ohm in/out, 0-300 lb., in tension only) with a TI AD620 instrument amp (5v power from data logger, gain resistor set for 5V out @ 300 lb. load). My data logger allows scaling the output appropriately for my application. Does this sound workable?

Edit: Got my notes mixed up. AD620 is by Analog Devices Inc, not TI.
______And I forgot to ask if supplying the same +5V to both the in-amp and the bridge is okay?

 

[Jack Gifford]

No need to answer my question- I'll power the amp with 12V and the bridge with 5V.

New question- Are S-type load cells made with mechanical internal stops to prevent over-stressing the strain gauges?
I wonder if I did harm by applying a 136 Kg force (tensile) to a 100 Kg-rated cell?

 

[Jack Gifford]

Torque measurement system completed, calibrated, and tested. All is well- cell wasn't damaged by overload.
Thanks.

 

[waross]

Thanks for the closure Jack.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[gruntguru]

Overload capacity of load cells is typically at least 150% x FS.

je suis charlie

 

[Balemon]

The strain gauge rosettes can be divided into three types: rectangular rosette (measures deformations in the multi-axis state), T-rosette (measures biaxial stresses), screwed rosette (measures torsion samples). But you need to know how to use strain gauge.
The strain gauge should be properly prepared by ideally gluing the strain gauge to the material being tested. The glue used should be specially prepared for use in the strain gauge. Its thickness should not exceed 10 micrometers. The operation of the glue should isolate the wires from the material being tested. The glue should withstand high operating temperatures without changing its physical and electrical properties. After proper gluing of the strain gauge, the whole system is covered with a protection layer, it may be a wax.