Loadcell wiring question

Thread Starter

niterida

Joined Dec 27, 2019
16
Are these 2 wiring setups identical ? For me I think it will be easier to wire it up with the modified (top left) version if it is the same ?

3 wire loadcell to 4 wires.jpg
Thanks :)
 

Thread Starter

niterida

Joined Dec 27, 2019
16
hi nite.
When you say load cell, do you mean a strain gauge 'element', or half bridge.?

Look at page #5 of this PDF.
E
Its a loadcell / strain gauge : https://www.robotgear.com.au/Product.aspx/Details/1728-Load-Sensor-50kg
I got the original diagram online to turn the 3 wire output into a 4 wire output required for my INA122 amplifier.
I currently have it all wired up with a 4 wire loadcell and this new loadcell is a straight replacement for it.
That PDF you linked means nothing to me :(
 

ericgibbs

Joined Jan 29, 2010
12,902
hi,
Checked your link, its a 'half bridge'.
So as you say you need two resistors adding across the Vext wires Red and Black.
The junction of the two resistors is connect to A-.,, the White wire to A+.

Its important that the two resistor are exactly the same value, otherwise you get a large offset reading on the Scale.

The usual way to get around this is to have two identical resistors connected to the ends of say a 100 ohm trim pot.
The wiper of the trim post is connected to A-.
So when there is no weight on the scale the trim pot is adjusted to give a zero weight reading on the scale.

Do you follow OK or would a sketch help.?
E

Added: Circuit option.
 

Attachments

Last edited:

Thread Starter

niterida

Joined Dec 27, 2019
16
I just need to know if both of those diagrams are the same - I have no knowledge of electronics and just going to copy the bottom one (which is correct for my application) but would be easier for me if I can do it the same as the top one.
thanks again
 

ericgibbs

Joined Jan 29, 2010
12,902
hi
Either would,
But remember the caution about the resistor values being matched, else a big weight offset error.

Keep the wires as short as possible, to avoid electrical noise pick up on the weighing signal lines.

E
 
Top