We’re rewarding the question askers & reputations are being recalculated! Read more.

New answers tagged

0

In terms of practical theory, all components have the ability to add noise, from reacting to external (emi) and internal (heating) sources of input you don't care for. Nothing changes instantaneously so everything has some frequency-related characteristics. As a general guess, yes several identical stages do tend to result in lower noise than something ...


0

BSEE, I struggled for some time with a similar issue that turned out to just be poor probing technique with a single ended oscilloscope. I wrote up the resources/techniques to clean up the measurement in this answer: Massive pk-pk ripple on output using isolated DC-DC converter module You may find as glen_geek said that the issue is not as severe as it ...


0

The transient comes from the control loop of your AC DC converter. Unfortunately the only way to eliminate this is to tighten up your control loop. But Why? The transient only lasts for some microseconds. This would not cause any damage normally. A decoupling capacitor across the rails would provide the protection. A varistor can also be used instead. Also ...


0

Can I get rid of these noises by using a high-pass filter? Can you reduce noise by using a filter? Yes. Can you "get rid of" (completely remove) the noise? No. There will always be some noise left. The important question to answer is: How much noise can you tolerate. Also: if the circuit generates more noise than what you can tolerate, how can that be ...


1

They are all DC errors that may contribute to a significant DC error on the output signal. I say "may" because this depends on the actual circuit implementation and (some) component values. Can I get rid of these noises by using a high-pass filter? Some of these DC errors can drift with time so, using a high pass filter with the wrong values may not ...


0

When you think of the noise figure of each individual block, you assume that the input noise is purely the thermal noise floor. The level of the input noise is important in the definition of the NF, otherwise you would get different numbers for NF depending on the value of the input noise, since the noise internally produced (Np) is constant. When you start ...


1

Most interfering noise on a cable is coupled equally to both conductors when certain cabling precautions are taken and these are twisting pairs (to reduce magnetically induced effects) and screening (to reduce electrically coupled effects). But, to ensure you handle correctly the common mode voltages on both conductors in a pair, you need to have a balanced ...


0

Consider this drawing of two circuits; the 2nd circuit has many intentional IMBALANCES. These imbalances degrade the DC CMR and the AC CMR. Notice the first circuit has gain of 1. Notice the 2nd circuit has gain of 1,000. simulate this circuit – Schematic created using CircuitLab


0

I reproduced your circuit in LTspice (except for using LT1007 op amps as I do not have a model for the OP1177) and got the same results. Then I replaced U1 and U2 with resistors and drove the optocoupler open loop. Noise dropped from 2.2µV/√Hz to 1.6µV/√Hz (with negligible contribution from the resistors). Finally I replaced the optocoupler with a current ...


0

You have several 200k resistors; for a first pass analysis, simply add those, to 400 kohm; for easy math round to 1 megaohm; that has noise density of 4 nV/rtHz * sqrt(1,000,000 / 1,000) = 4 * sqrt(1,000) = 4 * 31 = 124 nV/rtHz.; some resistors have "excess noise" from Pauli Exclusion quantum effects; use metal-film resistors, not those with carbon granules. ...


6

It looks like aliasing of some higher frequency signal (perhaps mains frequency). Compare your sample rate to mains frequency and other relatively high frequency noise sources.


1

I've two suggestions for you. 1) Run separate power and earth wires (as thick as possible) between the power supply and each of the LED and servo driver boards so that they don't share any power wiring. 2) Get a couple of large ferrite beads designed for noise suppression and thread each of the supply wires through them, maybe 2 or 3 turns. If you add ...


7

-3dB is the point of 50% power. The point when the tipping point changes from a majority of the power to a minority of the power gets through. The native form of the equation is: $$ SNR=10\log_{10}\left(\frac{P_{SIGNAL}}{P_{NOISE}}\right) $$ Power is proportional the square amplitude (think \$P= I^{2}R\$ or \$P = \frac{V^{2}}{R}\$). Which is why if you use ...


0

The path highlighted in red on your schematic carries pulsed recritfier currents: Do not connect your circuit ground along this path! It will be noisy. The correct place to connect supply ground to your analog circuit's main ground plane is the blue circle on the right. It may be beneficial to add a small capacitor (like 100pF) between the barrel connector'...


1

lets compute a magnetic-field interference, across 5 centimeters separation between the power region and your "highly sensitive" region. We will compute an "induced voltage", using some reasonable assumptions. If the computed voltage is much smaller than your measurement budget, then you should be OK. Otherwise you get to put on your engineering hat. We ...


3

Return current will be mostly in the shield of your coaxial cable, but that's not the problem. The problem is any changing magnetic field through that ground loop (the co-ax shield and the two ground connections) will induce a current that flows in the co-ax shield and that current will cause a voltage that looks like a signal to the receiver


0

Electrons explore ALL possible paths and take ALL paths, proportional to 1/impedance. Did I not clearly write ALL possible paths, including thru the air as displacement-currents, and thru that 6 meter longer path around the framework of the card-cage. ALL possible paths. Why is this? because this exploration, and exploitation, of ALL possible paths is how ...


0

Could be several things: 1) The wall adapter is junk. Older SMPS are known to be noisy. Newer SMSP like Mean Well LED supplies are known to be very good and can be very quiet. 2) Even if the SMPS is the modern good variety, they may not "like" large capacitors directly on the output. The ideal scenario is to use a common mode choke that is as large as you ...


2

In any non-josephson-junction ADC, you will have analog comparators; their bandwidth likely will set the noise floor. How to estimate the noise of the Comparator? simply use the input FET gate capacitance. Using sqrt(K * T /C), the math behind switched-cap-sampling-noise, you'll find a 10pF capacitor produces 20 microVolts RMS noise. And a (more likely to ...


0

The proper way to provide an input low-pass filter is to do both. The first case provides common mode filtering, and the second case provides differential mode filtering. To calculate the filtering needed, determine your Fc for the common mode case, where Fc = 1/(2 * Pi * R * Ccom). For the differential case, you simply add C4 (Cdiff) between the two inputs....


0

You must define the noise spectrum by risetime, pulsewidth at 50%V. Relevant Irrelevant -------------- ---------------- trace nH/mm signal frequency trace pF/mm coplanar vs vertical thin prepreg 5V-0 for C controlled Z 66 Ohm +/- 2W/L ceramic caps* Murata Decoupling SRF, PRF and ESR optmized to match ...


0

I would attempt to lower the ESL of the high frequency signals as it is inductance that blocks high frequency. I would double the vias of the decoupling capacitor to take the via inductance in half. I would also use an X2Y capacitor with much lower ESL (and ESR), they short high frequencies out much better than normal capacitors. I would also try an locate ...


3

"tick" sounds are usually created by something close to an impulse, or with a significant portion of impulsive energy. And time domain impulses create broad or wide-spectrum noise in the (FFT) frequency domain. So you are unlikely to be able to find or remove the majority of this noise with a generic (LTI) filter, such as an EQ or a notch. If the sound ...


0

You shouldn't just use some rough noise density number for this calculation. The reference fig for noise in your datasheet is Figure 10. From the datasheet you linked to: Noise density figures like this show a knee, below which pink low-freq noise dominates the white noise, and above which, white noise. The important parameters are the frequency of the ...


2

Input is signal frequency is 100Hz. I want to use the 6.5nV/sqrt(Hz) but it seems to be a spectral density, and I can't add it to a voltage This is where the bandwidth of the analog system comes in, the max bandwidth determines the noise. Let's say it's an ADC with a low pass filter at 1000Hz. The ADC would see: (1000Hz)^(1/2)*6.5nV/sqrt(Hz) = 2.05uV-rms ...


3

Input filtering is a must. In addition to that I find it a must to use at least a full GND plane when dealing with switching regulators. Along with a full GND plane you can have much better routing for the other power connections. Some additional things to go along with that: Use every effort to keep all of the VSW connections as clustered together and as ...


Top 50 recent answers are included