Hello.

Is it posible to connect 10 load cells to the WP231 using 3 junction boxes?

So far I have only been able to  find a schematic for 8 load cells using 2 junction boxes:

Can I plug a 3rd junction box to expand up to 12 load cells?

In case yes, and assuming I have 10 single load cells of 500ohms +- 15ohms, I should look for the next safety:

495ohms / 10 load cells = 49.5ohm. 

I think this should work right?

Finally. How does the WP231 reads the measured value of multiple load cells using the junction box? I assume it reads one load cell at the time until it scans all of them, and then it repeats the cycle. Is this correct? How often does the measured value from each cell is updated to the WP231?

If you can point me to an example of WP231 with 10 or 12 load cells will be terrific.

Thanks a lot for your kind help

Regards

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Split from WP231 multiple load cells?.

Hello jorgealfredo.js,

Yes, it is possible to connect 10 of your load cells to one SIWAREX WP231

The limit is the result resistance of all connected load cells together must not be lower than 40Ω.

In your case with 500Ω +/-15Ω the worst-case calculation is 485Ω/40Ω=12.125, that means that a max. of 12 load cells can be connected to the SIWAREX WP231 at the same time.

If you want to connect 10 load cells to one SIWAREX WP231 you must connect 4 junction boxes together like in your attached picture. To each junction box you can connect 3 load cells, except the last one there you can connect 4 load cells.

All load cells are electrically switched in parallel so the signal lines will show the mean value of all load cells in parallel. The SIWAREX WP231 evaluates only one signal.

The SIWAREX WP231 can not evaluate the signal of each single load cell.

If you need/want to evaluate the individual signals of each load cell you can connect the digital junction box to the SIWAREX WP231, see https://support.industry.siemens.com/cs/ww/en/ps/26025.

With the SIWAREX DB a max. of only 4 load cells is possible.

Regards

ABenno

Thanks a lot for the reply.

Just to be extra sure on my side. 

I want to read the weight of 10 different scales (0 to 10kg) using 10 different load cells (one load cell per scale). That information must go to a S7 1200. 

My best option, if I understand correctly, is to use 3 Siwarex WP231 each with a terminal box Siwarex DB and 4 load cells attached to 2 of them, and 2 load cells attached to the third terminal box. Then the 3 WP231 are connected to my S7 1200 right?

According to the needs I have, can you validate my approach to this weighting issue, and if available, suggest a different (maybe better) approach?

Thanks again.