Problem with INA125

Other Hardware Sensors
1

Hey Guys,

I'm trying to amplify the output of a load cell.
I'm using two half-bridge load cells, which means they only have got three wires. They look like this

I found this circuit on the internet, showing me how to wire up the INA125

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Vout+ and Vout- are the grey wires (first img) from the load cells.
My Voltmeter is connected to the 10th pin of the amplifier and the ground. It displays 70 mV and this value doesn't change by applying force to one sensor.

Are my sensor not compatible with the INA?

2

The connections are for a four wire load cell, yet you have a three wire load cell. I don't understand from your description how you have connected it to the amplifier. You might look through this series of posts: arduino - How to wire up a 3-wire load cell/strain gauge and an amplifier? - Electrical Engineering Stack Exchange

3

I wired it like this:

4

If you hope to get a helpful and informed response, you really need to provide some basic (correct) information. We aren't mind readers.

What did you use for Rg, which sets the amplifier gain?
What are the two voltages at the load cell outputs?

5

I'm not sure what Rg i should use. The lowest i have is 220 ohm.
The output is about 2.444 V each.
The resistant of the load cells is 2k ohm on the red and black wire and 1k on the grey and the red or black.

6

Your wireing may not be correct.
I guess the loadcells give 2.5V when fed 5V and not loaded?
If this is the case, wire them so that "+" and "-" are different.
This make output voltage increase a litte for one and decrease for the other
It is this small voltage (measure it with ) your multimeter (i guess <100mV when max load)
connect thees two wires to pins 6 and 7 with the higher voltage to pin 6
You want 4.5V max ? => gain 50 => Rgain=1k2 or 1k5

The INA125 is expensive. I use 8pin DILs, rail to rail opamps for tasks like this.
TS912IN / MCP6002ip are good alternatives. 4 resistors (and a trimmer ) to set gain.

7

Hi guys
I have 2 load cells sen10245 of 3wires (Red, white & black) each.
Please tell me how to connect it by using HX711(24bit ADC)

or how to connect with INA125P?
please send me circuit diagram connections.
Thnx

8

You normally connect one half-bridge upside down so that two half-bridges' output voltages
move in different directions as they are loaded up, so that the output represents the sum or
average of the load on both cells, not the difference (which is what your circuit gives).