[Solved] Help with instrumental amplifier + arduino analog input

Hi folks!

I trying to create a digital turbo meter to my auto. But I having dificulties.

First, I mounted a circuit identical to this (instrumental amplifier) to read data from pressure sensor: http://www.practicalarduino.com/schematics/water-tank-depth-sensor-schematic.jpg

So, using multimeter, it's allright. Vout is perfectly that I want, amplified and inside arduino analog input range (0-5v).

But, when I plug Vout on arduino, it's don't works. :(

Using multimeter, connecting red picker to circuit Vout and negative picker to GND on arduino board, I have 0v (zero volt).

Otherwise, when I plug red finger to Vout and black finger to negative of my external supply voltage, it's perfect (~0.9v to 2.2v)

I'm confused. Because the instrumental amplifier have only 1 positive output...

thanks in advance.

  • sorry by my english.

Using multimeter, connecting red picker to circuit Vout and negative picker to GND on arduino board, I have 0v (zero volt).

Otherwise, when I plug red finger to Vout and black finger to negative of my external supply voltage, it's perfect (~0.9v to 2.2v)

You need to connect the ground from your external supply voltage to a arduino ground pin, I think you will then see that the arduino analog input pin will read the output from your circuit correctly.

Lefty

Do you have all the GNDs connected together?


Rob

OMG! Now works perfeclty!

retrolefty and Graynomad, very thanks men!!!!!

  • sorry by my dumb question... I'm a newbie in electronics :D