Blur Busters Forums

Hi y'all, so today arrived an EMI meter and an EMI "filter" and the readings are quite interesting and revealing. For reference, I read somewhere that the ideal reads should be below 50mV.

Meter plugged to the outlet: 120-130mV

Meter plugged to the outlet with Filter also plugged: 110-130mV (looks like it doesn't do much)

Now here comes the interesting part:

Meter plugged to the outlet WITH PC ON: 1400-1500mV

Meter plugged to the outlet with Filter also plugged WITH PC ON: 1000-1100mV (looks like it filters when the interference in the electricity is too big)

This is quite revealing and it would pretty much explain why I have input lag, what I still don't know is why my PC is messing up so much with the electricity, faulty component? Who knows...

PC OFF READINGS VIDEO

https://youtube.com/shorts/ZJII4wrpNWg?feature=share

PC ON READINGS VIDEO

https://youtube.com/shorts/6iM_4UYzyqY?feature=share

I reached 100-125 mV with the PC on. There was absolutely no difference between 1850 and 100-125 mV. In any case, this could indicate a problem. But honestly, I don't think this is the problem. What is the frequency range of your tester?

You do know that the EMI filter measures only within a certain frequency range, right? So this isn’t the full picture, but for example from 25 kHz to 100 MHz, or something like that.

Slender wrote: ↑

07 Jan 2026, 15:26

I reached 100-125 mV with the PC on. There was absolutely no difference between 1850 and 100-125 mV. In any case, this could indicate a problem. But honestly, I don't think this is the problem. What is the frequency range of your tester?

How did you get it to 100.125 mV with PC on? Filters? Also my meter rannge is 10KHz - 10MHz

ablemor wrote: ↑

07 Jan 2026, 15:28

You do know that the EMI filter measures only within a certain frequency range, right? So this isn’t the full picture, but for example from 25 kHz to 100 MHz, or something like that.

I know that, but what's your point? It's giving readings

Roxtar wrote: ↑

07 Jan 2026, 16:30

Slender wrote: ↑

07 Jan 2026, 15:26

I reached 100-125 mV with the PC on. There was absolutely no difference between 1850 and 100-125 mV. In any case, this could indicate a problem. But honestly, I don't think this is the problem. What is the frequency range of your tester?

How did you get it to 100.125 mV with PC on? Filters? Also my meter rannge is 10KHz - 10MHz

that was a psu what not emit in AC. (it was aerocool 650w, i dont remember model).
+ using a toroidal transformer.
What I noticed:
1) When psu is inserted into the ac network (switch button on, but not power on), the mv value may be lower (the psu cleans the ac line).
2) If you insert a filter with the reverse side between the transformer and psu (that is, swap line and out), the mv on the tester becomes smaller when the PC is turned on. If you set the filter correctly line-out, the mv on the tester will not decrease, as well as there will be no improvements on the screen.

Roxtar wrote: ↑

07 Jan 2026, 16:31

ablemor wrote: ↑

07 Jan 2026, 15:28

You do know that the EMI filter measures only within a certain frequency range, right? So this isn’t the full picture, but for example from 25 kHz to 100 MHz, or something like that.

I know that, but what's your point? It's giving readings

hes mean problem can be placed in different frequency, that is, not in the range that your tester shows.
my tester shows 10khz-10mhz, and no improvements, when it 1850 or 100. I mean, exept what im write about cheap emi filters reverse mode.

Slender wrote: ↑

07 Jan 2026, 15:26

that was a psu what not emit in AC. (it was aerocool 650w, i dont remember model).
+ using a toroidal transformer.
What I noticed:
1) When psu is inserted into the ac network (switch button on, but not power on), the mv value may be lower (the psu cleans the ac line).
2) If you insert a filter with the reverse side between the transformer and psu (that is, swap line and out), the mv on the tester becomes smaller when the PC is turned on. If you set the filter correctly line-out, the mv on the tester will not decrease, as well as there will be no improvements on the screen.

I see, that's quite interesting as well, but still, ideal value should be below 50mV, videos in YouTube showed people going from 100mV+ to 20mV and I think that's where improvements will show, let's say anything above 100mV is bad and any mV decrease above that mark is unnoticeable.

Roxtar wrote: ↑

07 Jan 2026, 16:50

Slender wrote: ↑

07 Jan 2026, 15:26

that was a psu what not emit in AC. (it was aerocool 650w, i dont remember model).
+ using a toroidal transformer.
What I noticed:
1) When psu is inserted into the ac network (switch button on, but not power on), the mv value may be lower (the psu cleans the ac line).
2) If you insert a filter with the reverse side between the transformer and psu (that is, swap line and out), the mv on the tester becomes smaller when the PC is turned on. If you set the filter correctly line-out, the mv on the tester will not decrease, as well as there will be no improvements on the screen.

I see, that's quite interesting as well, but still, ideal value should be below 50mV, videos in YouTube showed people going from 100mV+ to 20mV and I think that's where improvements will show, let's say anything above 100mV is bad and any mV decrease above that mark is unnoticeable.

well, I think the jump from 1850 to 100 should give at least 5% improvement, but it didn't happen. By the way, the UPS of the inverter gives 1600mv, while the sound noise is quieter than from the same ac 1650mv network.

The frequency range is important because if the measurement shows low EMI in that range, then the problem is not in that frequency. Otherwise, the issues are likely to occur above 1 GHz.