Hi, I got myself an MCP6002 to measure a voltage that was too small for the arduino scale. However when I wired the circuit as in the specs sheets, the Vout that I measure is the Value of the Vdd (5volts). Any idea why is not working? Do you think it may be broken? Thanks, Luis

Unfortunately we need more information. Have you measured the input voltage to the op amp with a meter? How much gain do you have? Give us the values or R1 and R2.

Hi, Thanks for your message. I am using an R1 of 100 kohms and R2 10 kohmsn for a gain of 101. I am measuring a voltage drop across a resistance. When it is at is lowest is 0.2 mV (measured with a multimeter). Still i am getting the maximum voltage . Thank you, Luis

I am measuring a voltage drop across a resistance. If one end of the resistor isn't grounded, you might have a ground problem... So, we might need to see the circuit with the resistor and we would need to know if it shares a common ground with the Arduino. Typically, you need to totally isolate …

100k and 10k as a noninverting amp is a voltage gain of 11, not 101. Can you show us a schematic?

That op-amp has an input-offset range of +/-4.5mV, so you won't be able to measure 0.2mV with any accuracy.

Don't forget that offset voltage gets amplified, too.

polymorph: 100k and 10k as a noninverting amp is a voltage gain of 11, not 101. Can you show us a schematic? Hi, Thank you for your message. You are right about the gain. I am attaching a schematic. Thanks, Luis [mcp6002 wiring_bb.jpg]

I am attaching a schematic No you are not. That is a physical layout not a schematic. Why are you only powering it with 3V3?

I think the Op Amp can work at 3.3V . or 5 V should be fine too. I hope this is the one image needed . Thanks, Luis [pin position MCP6002.png]

think the Op Amp can work at 3.3V . or 5 V should be fine too. Yes but if you wired it like you said then there is no way it will output 5V, like you said you saw. A schematic is what you wired not some page off a data sheet. Face it you are doing something wrong, we can only help you find that…

Wirign of a Op-Amp MCP6002

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dc42 August 20, 2013, 10:21am 12

I suspect that your main problem is that the "circuit pulling current" does not have a common ground with the op amp and the Arduino.

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Wirign of a Op-Amp MCP6002

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