Arduino Analog read problem

[Achira]

HI,

I use arduino to read a sensor (Antenna) value. we measure from a oscilloscope that antenna values. we got that the maximum value or peak value is some what 200 mV. But the analog read value gives 1023 read as peak. when i give 5 v to the that pin then it gives 1023 also. what is the problem. Can you help me?
Here i attached the arduino readings and the screen shot of the oscilloscope.



View attachment 230V-1A - 0cm .txt

 

[wp100]

Hi,

You cannot read a sine wave on an ADC pin just like that; just think about it, what is the frequency of the ADC sampling the Arduino does ? how can that match the peak of the pulses from your Antenna ??

Do some web /arduino searching and you will find how you need to 'condition' the signal before you can read it via the ADC pin

 

[Achira]

thanks,
this signal is 50 Hz. can't i use arduino to measure this?

 

[KlausST]

Hi,

If understnd this right, then you only have a piece of wire connected to your adc input. Is this correct?

Then the input acts like "floating". This means the value is somehow undefined. A scope has a defined impedanc to its GND.
Be sure that the scope and the adc refer to the same gnd potential.

Reading an adc value with only a piece of wire will not give any meaningful values.

If you want to see some "funny" adc readings the use two 1Mohms resistors one from gnd to adc input, the other from vcc to adc input.

Klaus

See what happens.

 

[Achira]

Hi,

If understnd this right, then you only have a piece of wire connected to your adc input. Is this correct?

Then the input acts like "floating". This means the value is somehow undefined. A scope has a defined impedanc to its GND.
Be sure that the scope and the adc refer to the same gnd potential.

Reading an adc value with only a piece of wire will not give any meaningful values.

If you want to see some "funny" adc readings the use two 1Mohms resistors one from gnd to adc input, the other from vcc to adc input.

Klaus

See what happens.

yes, we use single wire connected with small copper plate.
and we get some crazy values.
please tell me how we can get this in proper way. should we have some any filter or something before connected to the antenna.
please reply me ASAP. i am in very critical situation.

thank you very much.

 

[KlausST]

Hi,

what is this for?
What do you expect?

Please try to describe it as detailed as possible with all the values you know or try to achieve. A technical description.


Klaus