load cell signal conditioning

jayanthi k

Other Parts Discussed in Thread: OPA2277, XTR106

Hi,

I am in the process of designing loadcell. . I am using a Wheatstone bridge circuit to detect the difference in my voltages with the weight differences. I am using two strain gauges both 350 ohm and two 350 ohm precision resistors. I am using the opa2277 and xtr106 as my amplifier and VtoI converter.I have connected my circuit as per xtr106 datasheet application note.

My problem is when i connecting opa2277 output to xtr106,then it is loaded.i.e opa2277 output is 415mv means,after connected with xtr106 it is reduced to 15mv.kindly suggest me.

Thanks for your help

jayanthi

over 12 years ago

0 Yingying Sun over 12 years ago

TI__Intellectual 1155 points

Hi, Jayanthi

It looks like you build your circuit like Fig 5 in the datasheet. Can you share your schematic so we can check them for correctness? It helps if you provide PCB too.

From the structure of XTR106 on page 4 of datasheet, we can see that the input stage are non-inverting pins of op-amp. They are high impedance so it is strange that connecting the output of OPA2277 to them would cause the output to decrease.

Please share your schematic and we'll get this solved.

Regards

Janet Sun

0 jayanthi k over 12 years ago in reply to Yingying Sun

Prodigy 20 points

Dear sir,

pls find the attached circuit.

0 Yingying Sun over 12 years ago in reply to jayanthi k

TI__Intellectual 1155 points

Hi, Jayanthi

Can you send the actual schematic that you have used for your design and a picture or image of your PCB / bread board circuit? If you use lower impedance bridges, make sure the excitation current to ≤ 2.5mA.

If you connect things as shown in the datasheet then the circuit will work. So please send us your actual circuit connections so we can debug your issue.

0 Johan andreson over 12 years ago in reply to Yingying Sun

Prodigy 20 points

Really good source for getting info about the correct usage of strain load cells and really impressive practically. Plz share some more details about canisters and cross beams also.

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load cell signal conditioning