so, then, using ground rods to elimanate noise could actually work depending on the noise that is causing the problems ? I wonder what the cut off frequency is for using the earth as a filter, and if its ever useful for the type of noise that generally causes problems with electronic equipment ?
electrical noise
- Thread starter electricalperson
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so, then, using ground rods to elimanate noise could actually work depending on the noise that is causing the problems ? I wonder what the cut off frequency is for using the earth as a filter, and if its ever useful for the type of noise that generally causes problems with electronic equipment ?
Speedskater
Senior Member
- Location
- Cleveland, Ohio
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- retired broadcast, audio and industrial R&D engineering
Probably not!
a) There is a whole lot of difference between a 3000 foot ground system and an 8 foot ground rod.
b) The earth ground is not a major factor in noise problems. The noise current will not just flow into the earth and go away. Earth only enters the equation when the noise current can't find a better path back to it's source.
ELA
Senior Member
- Occupation
- Electrical Test Engineer
Interesting Discussion
Interesting Discussion
When trying to lower noise levels we are trying to reduce the impedance between the source of the noise and its return path.
A zero potential ground plane being the ultimate goal.
Whatever can lower the impedance between source and the return path will help in theory. So I believe that ground rods can help, at least in theory.
We always attempted to lower the (ground) return impedance by using thick flat braided wire connected to building steel where possible. As a supplemental high frequency return path.
Here is an interesting link that speaks to the question about the conductance of the earth with frequency.
http://soil.scijournals.org/cgi/content/full/68/5/1515
If you want to skip ahead to the conclusion there are some good graphs there.
Many people tend to think only of the low frequency paths (60hz) and fail to consider that electrical noise is often a high frequency event.
Interesting Discussion
When trying to lower noise levels we are trying to reduce the impedance between the source of the noise and its return path.
A zero potential ground plane being the ultimate goal.
Whatever can lower the impedance between source and the return path will help in theory. So I believe that ground rods can help, at least in theory.
We always attempted to lower the (ground) return impedance by using thick flat braided wire connected to building steel where possible. As a supplemental high frequency return path.
Here is an interesting link that speaks to the question about the conductance of the earth with frequency.
http://soil.scijournals.org/cgi/content/full/68/5/1515
If you want to skip ahead to the conclusion there are some good graphs there.
Many people tend to think only of the low frequency paths (60hz) and fail to consider that electrical noise is often a high frequency event.
- Location
- Bremerton, Washington
This is called by the NEC an auxiliary and does not have meet any of the nec requirements for grounding electrodes see 250.54
- Location
- Bremerton, Washington
Studies by the EPRI have shown a ground rod such as you describe can introduce more noise, or current (lighting) into the equipment as it creates a voltage drop from the ground rod to the main electrical ground, voltage drop = current flow.
I had the study and sent it to mike holt. He mad a graphic out of it in his grounding text
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