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Topic: 4-load cells (Read 3396 times)previous topic - next topic

hussain_sheikh Jan 09, 2015, 01:27 pm
Hi,
I have 4 load cells which calculate upto 200 kg each. i want to place them under the four legs of table and calculate the combine effect of them when load is placed upon them using arduino.
Load cell is of 4 wire
Red = E+
Black = E-
Green = S+
White = S-

Plz urgent help required...

AgeBee #1
Jan 09, 2015, 04:58 pm
You know how to connect them because we read your thread here: Load Cell INA125P

So having four of these guys is no other: Use four times the setup which you use for a single one and then calculate the average.

hussain_sheikh #2
Jan 10, 2015, 11:55 am
Using four times meanz i have to use four ina125p and four analogue pins..?

Agebee i still have some problem in setting gain (Rg)... can u guide me in setting that..?
whats the purpose of it..? What does gain do..? how it can be set in my case..?
i get this formula from ina125p for gain

G= 4 + (60k/Rg)
how it can be used..?

Thanks

groundFungus #3
Jan 10, 2015, 03:59 pm
What is the full scale output from the load cell?  The full scale output (FSO) should be specified in mV/V.  What is your excitation voltage?  What is the analog converter reference voltage? You need that info, at a minimum,  to know what the gain needs to be.  Rg is the gage resistance.  Can you link to the load cell datasheet or specifications?

And to find the weight of the table and contents you must SUM the load cells if there is a load cell under each leg.

hussain_sheikh #4
Jan 15, 2015, 04:11 pmLast Edit: Jan 15, 2015, 04:13 pm by hussain_sheikh
Attached is the data sheet .Mine cell is highlighted one.
Plz note i have 4 wires (Not 6)
Red = E+
Black = E-
Green = S+
White = S-

And to find the weight of the table and contents you must SUM the load cells if there is a load cell under each leg.
yes i need to SUM the load cells but cant understand what you mean by if there is a load cell under each leg

groundFungus #5
Jan 15, 2015, 06:38 pm
I meant under each corner.  The FSO is 2 mV per Volt of excitation.  If the excitation voltage is 5 V the output at full scale load from the load cell is 10mV (0.002 * 5).  Further, if the ADC reference is 1.1V you need a gain of 1.1/.010 = 110.  You must balance the bridge of the load cell prior to amplification.

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