how to use My Rio-1900 to read strain

[MD_Salem]

Hi everyone,

I am using My Rio-1900 to read strain using 120 Ohm 2-wires strain gauge , to condition the signal I used the attached circle which is mainly wheatsone quarter bridge consisted of 3 120 resistors and excited by + 5 DCv (from My Rio-1900),  then the induced signals between junction 2 and 4 is magnified by AD 620 as shown

My problem that no signal is shown by this circuit despite I double checked  the wiring and measured the resistance value of all component.

Would any one did it before show my how to figure such problem out ?

Regards

[Henrik_Volkers]

Circuit is missing 😉

Start with a Gain setting of 1 (no Rg) , do you read 2.5V?

However: Do you have a Multimeter to measure voltage?

Check the two bridge outputs to GND, they should be around 2.5V 

Now check the voltage across the bridge output , should be around 0V to some mV, shouldn't be too much , otherwise the AD620 is (depending on the gain) on it's limit and just sitting near 0V or 5V.  

A simple way to null the bridge is a modification of one your bridge resistors to zero the bridge by paralleling it with another resistor, or you add a 10k potentiometer from GND to 5V and a resistor of 1k to 47k  (depending on the amound of adjustment needed) from the wiper to the bridge output of your two 120R ... 

[Henrik_Volkers]

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@Henrik_Volkers wrote:

Circuit is missing 😉

Start with a Gain setting of 1 (no Rg) , do you read 2.5V?

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Don't need to be 2.5V .. depends where you put your Vref on the INA 😉  however it should be some mV close to your Vref. But if you put Vref to GND the INA can't measure negative values, since it can only outut voltages close to it's negative supply voltage (exact value is in the datasheet).   So schematic is  helpfull 😄

[MD_Salem]

I could read a signals but they are destroyed by noise.

The attached circuit is what I used and the  screen shot of some signals 

How do you think I can get ride of this noise ? , I tried to apply FFT and then isolate the noise frequency with some filter but the results were not the  best 

Regards