Hi guys

I have some trouble understanding a load cell, take this one for example:

http://edg.uchicago.edu/tutorials/load_cell/FX1901.pdf

I don't know how to work out the voltage output and force/weight ratio.

what does mV Output: 20 mV/V Nominal mean in the datasheet? I am kind of expecting xyz Newton or Kg / mV or something.

but all the tutorial I read need to put a known weight and work out the weight/mV ratio.

 

it means at full scale, it will give you 20mV for every 1V you apply to it.

So if your load cell is rated 200LBS max and you apply 10V of excitation current, and you load it with the full 200LBS, it will output 200mV.
(100% load X 10V X 20mV/V)

If you load it to 50LBS you will get 50mV
(25% load X 10V X 20mV/V)

 

it means at full scale, it will give you 20mV for every 1V you apply to it.

So if your load cell is rated 200LBS max and you apply 10V of excitation current, and you load it with the full 200LBS, it will output 200mV.
(100% load X 10V X 20mV/V)

If you load it to 50LBS you will get 50mV
(25% load X 10V X 20mV/V)

Thanks now I understand, I think you mean 10V of excitation voltage above as well?

Another question, are all the s beam load cell expensive? I am looking for a s beam load cell, be able to handle +/-500N, they are like over $4-500, are there any sub $100 ones? I don't need very high accuracy.

 

yes, look at ebay and amazon. I was looking at sub-$100 load cells recently

 

http://www.ebay.com/itm/Parallel-Be...471?pt=LH_DefaultDomain_0&hash=item27d2201527

 

Read note #1 in that pdf: The output is a ratio of the supply voltage. So if full scale is 20mV/V and you supply 5V, AND the full scale is 100lbs, you'll get an output of 1mV per pound.

Oops, should've refreshed first.

 

Ah yes load cells can be tricky for the beginner to understand. Load cells like the one you have have need a excitation voltage. And the output will a differential readout across the bridge. So the the 20mV/V means for each volt used as excitation voltage. The differential reading at full load will be 20mV times excitation voltage. Using 1 volt as excitation the differential output reading will be 20mV using 2 volt 40 and so on.
http://www.sentranllc.com/pdfs/tb_accu.pdf

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What are the different with these two type of load cell, they both seem to do what I want, tension and compression measurement:

Round one
http://nz.element14.com/newport-electronics/lc201-300-n/sensor-load-cell-300lb-2mv-v/dp/2357236?in_merch=New%20Products

S Beam type
http://nz.element14.com/newport-electronics/lc101-500-n/sensor-load-cell-500lb-3mv-v/dp/2357235?in_merch=New%20Products

 

both of those are >10X your budget

 

both of those are >10X your budget

I know, I am just curious, want to know the different why there are two type. Not that I am going to buy those.

 

What are the different with these two type of load cell, they both seem to do what I want, tension and compression measurement:

Round one
http://nz.element14.com/newport-electronics/lc201-300-n/sensor-load-cell-300lb-2mv-v/dp/2357236?in_merch=New%20Products

S Beam type
http://nz.element14.com/newport-electronics/lc101-500-n/sensor-load-cell-500lb-3mv-v/dp/2357235?in_merch=New%20Products

It looks like the round ones are smaller in size, am I correct?