Eliminate high frequency noise from circuit

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shaswat

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I have an single phase electronics energy meter that working good in normal condition. But if I put some device that produces high frequency pulse then my meter starts resetting. The device (called Jammer) is producing a very high frequency pulse that resetting the device instantly so the only option is to immune the meter to that frequency. First I thought that to detect the high frequency pulse but it is not possible. So what I have to do to eliminate these high frequency pulses from meter. I used some good insulators that resist these frequency but that is not sufficient so restrict these noise.Is there any way to use some good capacitors that directly ground those frequencies. I used varistor diode and TVS diodes but that's not helping.

Please tell me that is there any way to immune my meter from these frequencies?

any new idea would be appreciated....
 

In addition to the advice that crutschow gave concerned to circuit scope, you could improve noise immunity focusing some attention at layout shielding attributes of the design, not only restricted to PCB, but also to case assembly.



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I have already use RC circuit but its not helping. Already tried to shield the device with the good insulators that restrict the high frequency. Using good insulator shiled helps me upto 10 to 15 sec but after that it fails.

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andre_teprom said:
In addition to the advice that crutschow gave concerned to circuit scope, you could improve noise immunity focusing some attention at layout shielding attributes of the design, not only restricted to PCB, but also to case assembly.



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Click to expand...
I have already use RC circuit but its not helping. Already tried to shield the device with the good insulators that restrict the high frequency. Using good insulator shiled helps me upto 10 to 15 sec but after that it fails.
 


Hi shaswat

Add your schematic and deliver more information .
Snubbers and Some kind of filters can help but trying to find noise source and suppressing that would be more reasonable .

Best Wishes
Goldsmith
 

Metal shield or box for could help. Aluminium foil wrapped around energy meter is simple solution.
 

Borber said:
Metal shield or box for could help. Aluminium foil wrapped around energy meter is simple solution.
Click to expand...

I tried to shield the meter from the sheet but no doubt it resist but not more than 10 to 15 second, after that meter starts resetting. The thickness of the sheet is 1mm. Using more than this thickness would be not saleable.

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View attachment Schematic.pdf
goldsmith said:
Hi shaswat

Add your schematic and deliver more information .
Snubbers and Some kind of filters can help but trying to find noise source and suppressing that would be more reasonable .

Best Wishes
Goldsmith
Click to expand...

Here is the attached schematic..................

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udhay_cit said:
Post your circuit for analysis. Use filter chokes, ferrite beads, etc...,
Click to expand...

Here is the attached schematic..................
 

I'm a bit unsure of where your noise is entering the meter from the description...
I dont know if you have worked that out yet but I see you have tried RC and shielding.
Given the word "jammer" maybe it's RF maybe not.
Perhaps if you started trying to quantify the noise (scope signal) you may get a better
idea of how to target this.
I have had luck in the past using instrument op-amps to build band pass filters
where noise is entering via ground or signal lines - maybe something like that
would be viable. Or perhaps a contact-less method of measurement.
If it is rf (that word jammer troubles me) the only answer would be really
good shielding (and careful PCB layout and construction)
 


Actually the jammer is nothing more typical but its just a RLC circuit. Its a combination of a 0.41 uF cap with scooter coil having 15 Kv strength. As you got from the schematic that we are also using some RC circuit but this combination is not sufficient.. I tried to shield my meter but that would be not sufficient and even if I increase the thickness of the shield then it would not be saleable. It generates some high frequency noise ( I measured it and its varied upto several Hz to 10 KHz) so the possibility of RF signal has been neglected.
 

I reviewed the schematic. In a brief, I don't understand the implemented EMI protection scheme.

You have non-ground nodes like analog supply V3P3A that are directly connected from outermost filter capacitors of measurement inputs to the energy meter chip. In addition, we need to get an idea of the circuit layout.
 

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