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Noise Reduction Techniques

:: EPE Chat Zone ­:: ­Radio Bygones Message Board :: » EPE Forum Archives 2010 - » Archive through 26 September, 2010 » Noise Reduction Techniques « Previous Next »

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muskrat
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Username: muskrat

Post Number: 303
Registered: 06-2009


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Posted on Saturday, 25 September, 2010 - 02:23 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

My moisture sensor produces a 0-5V DC level proportional to the moisture level in the hydroponics bag.

Under normal "wetness" conditions, the level is approximately 2.5V.

The sensor probes are selected by a 2-wire transmission system, utilising pulses at a frequency of about 1KHz.

I have been getting inconsistent readings of the sensor voltage. Putting the 'scope to good use shows the actual level from the moisture sensor to be stable, but there is a certain amount of noise super-imposed on the signal. It looks as if these noise pulses are coming from the 2-wire signals.

The noise is present as pulses over a larger amplitude than the 2.5V level.

I have tried a simple RC filter but am still getting the noise.

How would I go about reducing the level of interference without compromising the integrity of the DC signal I require?

Brian
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gajjer
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Username: gajjer

Post Number: 338
Registered: 05-2007

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Posted on Saturday, 25 September, 2010 - 04:07 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hi muskrat
have you any idea where the noise is coming from?
Can you be more specific about what frequency, amplitude and waveform of the noise?

cheers
gaj
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muskrat
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Username: muskrat

Post Number: 304
Registered: 06-2009


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Posted on Saturday, 25 September, 2010 - 05:31 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

I'll scope the line with a bit more diligence in the morning and post the findings.

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