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"Random" noise and spurious values

1472 Views - Created 05/04/2016

05/04/2016

Posted by:
mteichtahl

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I am using the ADC DAC board to convert analog inputs from a wind speed meter. 

This setup is very simple with Vdd and GND connecting to the wind speed meter and the signal and GND from the wind speed meter connected to the ADC DAC board. 

I am seeing the following behaviour

1. When the input voltage is 0 the ADC output bounces around and never seemingly goes to 0. This is also observed with no input connected. 

2. I seeing regular, but not period, jumps to 255 regardless of the input voltage. 

Id like some advice on the best way to try and address this. Do I need some form of RC circuit on the input to hold the input for a little longer ? 

I have nothing nothing connected to the ADC DAC boards 3.3v or GND inputs and the VDD is not shared between the board and the wind speed meter. 

 

Any advice or guidance would be appreciated

05/04/2016

Posted by:
andrew

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Location:
United Kingdom

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The problems you are describing could be caused by noise either on the windspeed cable or on the 3.3V or ground line.  The ADC chip on the ADC DAC board uses the 3.3V rail as the reference so any flucuations in the voltage will appear as random numbers on the ADC reading.  Is the cable from the wind speed sensor going past any high voltage or AC cables?  If so then this could induce voltage spikes on the cable which would also show up as random bounces when the input should be at 0V.

Using an RC filter on the input may help to reduce the noise or an op amp active filter may work better as it would give a low impedance filtered output to the ADC.

Is the output from the wind speed sensor linear or pulsed?  If it is pulsed then you could use a comparitor circuit to set the input to trigger only above a set limit.

 

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