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Topic: Reading multiple analogue inputs using Arduino mega at 1000 Hz sampling (Read 73 times) previous topic - next topic

Melli

Hello Guys,

I am trying to read two analogue input data (Electromyogram signals (bipolar signal in nature)) using arduino mega at 1000 Hz sampling frequency. The analogue inputs are coming from the device called Biopac MP150 module(https://www.biopac.com/product/mp150-data-acquisition-systems/), which can give two channels of analogue inputs sampled at 1000Hz. These two analogue signals are then passed through two voltage divider circuit for giving a dc shift to it and the output of the voltage divider circuit is fed to the A0 and A1 pins of Arduino ( The circuit is given and the code is given).

But I not getting clean signal values at A0 and  A1. I find an interference between these two channels like one channel affecting the out put of other.

So I tried to use two different arduino mega for reading two analogue channels separately at two different COM ports. While I am reading one channel( one arduino) at a time the arduino serial monitor gives  correct values. But when I am using two different arduino mega to read two different channels, I observe the interference between the channels like both are reading similar values.

Kindly suggests something. I am unable to understand that how can the two analogue interfere wile they are connected to two different arduinos.

adwsystems

Your problem is likely in the hardware or the program. Neither of which we can see without sharing it with us.

The Arduino UNO has 6 analog inputs but only one ADC. When you read channel 1 and then channel 2, the ADC sampling circuit may still be charged with the voltage from channel 1. The easiest thing to do, is pre-read and through away a reading after changing channels and before you actually accept the ADC reading channel. I suspect you are not doing this but we will know better when you post the program and the wiring. So swing by the How To Use this forum thread to learn how to post your program and circuit diagram.

P.S. I have never seen a resistor divider shift the voltage of a bipolar signal. I can't wait to see this too.

pert

#2
Oct 16, 2018, 12:42 am Last Edit: Oct 16, 2018, 12:43 am by pert Reason: Rotate picture
Melli's picture from their duplicate post:
http://forum.arduino.cc/index.php?topic=573813


Melli, instead of wasting time creating a problem for the forum members and/or moderators with your duplicate post, why not instead respond to the person trying to help you?

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