I want to amplify a small voltage from a sensor within 0-25mv to 0-5v and send this signal to analoginput(Arduino).
I have used the instrumentation amplifier with 3 OP07.
The multimeter can correctly measure the voltage from instrumentation amplifier. But when I connect the output with Arduino, it just show the total wrong number.
For example, there is a small offset with 0.14V, I want to use software to remove that. Basiclly I need to see 28 or 29 from analogread()... But it shows always 0 for 2 secounds or 1023 for 3 secounds, meanwhile the multimeter shows still 0.14V.
Is there a too loud noise from instrumentation amplifier？
What should I do that analogread() can receive the right voltage from instrumentation amplifier?
I assume the instrumentation amp runs on a dual rail supply, e.g. +12volt and -12volt.
In that case, you can't connect the output of the instrumentation amp directly to an Arduino input.
The Arduino pin could get damaged by higher voltages than it's supply, and lower voltages than Arduino ground.
You must use protection resistors (voltage dividers) and maybe schottky clamping diodes.
And ofcourse, connect grounds.
Leo..
You don't say what sensor, or what you are doing with the signal other than 'use an Arduino'. That's ok, I will be similarly general.
Why are you using a 3 amp device with a 24 volt system (+12 to -12.) Perhaps you can start out with a single op-amp run between +5 volts and ground. It will be MUCH easier to experiment with, and less likely to give you 'mysterious problems'.
The signal will then always be between 0 and 1023 as read by an analog pin of the Arduino. You can easily adjust the gain from unity to many thousand times with resistors on the pins of the op-amp.
