Hello everyone, i am a newbie, now i got a project use MPX10DP. As i know this sensor like a wheston brigde, so i have a circuit like my picture under here. i want to calculate the diffirence between Vout+ and Vout- and gain it 50 using LM358. I haven't tested it at all. I wonder if my schematic will go fine or not? Can all u see and evaluate my sche ? sr i am not good at english

 

hi NDM,
Check the polarity connection of the MPX signal to the first amplifier.

E

 

"Normally" you would want to take G in the first stage. Also keep in
mind if you want minimum error the 100K R's must have good matching
and tracking in order to maximize CMR (Common Mode Rejection), all
reasons usually you do this with a IA (Instrumentation Amplifier) which is
laser trimmed on the production line.

More than you want to know about IAs (Instrumentation Amplifiers) -

https://www.analog.com/media/en/tra.../designers-guide-instrument-amps-complete.pdf

https://www.analog.com/en/education/education-library/linear-circuit-design-handbook.html


Regards, Dana.

 

hi NDM,
Check the polarity connection of the MPX signal to the first amplifier.

E
View attachment 164764

sorry, i dont know what u mean?

 

sorry, i dont know what u mean?

hi NDM,
Look at this marked up circuit image and compare the Input connections to the simulation I posted.
E

 

"Normally" you would want to take G in the first stage. Also keep in
mind if you want minimum error the 100K R's must have good matching
and tracking in order to maximize CMR (Common Mode Rejection), all
reasons usually you do this with a IA (Instrumentation Amplifier) which is
laser trimmed on the production line.

More than you want to know about IAs (Instrumentation Amplifiers) -

https://www.analog.com/media/en/tra.../designers-guide-instrument-amps-complete.pdf

https://www.analog.com/en/education/education-library/linear-circuit-design-handbook.html


Regards, Dana.

@danadak
thks for ur opinion, but my project need save the money as little as possible. In the older machine, i see they used OP07 to handle this problem and it is less accurate than LM358.
and can u tell me my sche has problem or not ? i want to hear ur opinion about it or suggest me other sche you often use

 

hi NDM,
Look at this marked up circuit image and compare the Input connections to the simulation I posted.
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i guess that u mean :
1. LM358 can use single supply(i dont want to take double supply so i choose LM358 because it is simple)
2. maybe output of my sche is negative voltage, so MCU can not read it.
right?

 

No, I do not mean that.

Look at the way the input wires from the sensor are connected to the amplifier in this image.

E

 

No, I do not mean that.

Look at the way the input wires from the sensor are connected to the amplifier in this image.

E

now i think i can understand correctly. But u only think my sche got only that problem ? how about i choose LM358. Can u evaluate my sche? is this a wise thing ? or i need change ?

 

hi,
Look at this LM358 version.
Input signal 20mV thru 60mV.
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