What is electrostatic noise and how does it affect analog and digital signals?

[treehouse]

I started an electrical engineering degree this semester. My book says that electrostatic noise meaningfully affects analog but not digital. But it does not say what electrostatic noise is, and neither Google nor Wikipedia readily yield an answer to this question: What is electrostatic noise?

 

[yungman]

You sure you are not refer to thermal noise(from resistance), flicker noise (1/f noise that is device dependent), current noise ( I don't remember the name! Too old!). Even DC current is not totally smooth as it sounds, it is only time average, at any instance, the current is not even and noise is produced.

 

[treehouse]

You sure you are not refer to thermal noise(from resistance), flicker noise (1/f noise that is device dependent), current noise ( I don't remember the name! Too old!). Even DC current is not totally smooth as it sounds, it is only time average, at any instance, the current is not even and noise is produced.

The book says 'electrostatic noise', a term which isn't even in its index. But I guess resistance does result from electrostatic forces (since subatomic particles, including those that compose different atoms, never really touch - its just their electrostatic fields that interact).

 

[yungman]

I have not heard about it don't mean it does not exist, I am no expert on noise. I remember now, the uneven DC current due to electrons passing through is called Shot noise.

 

[geneiusxie]

Electrostatic noise is caused by parasitic, or unintended, capacitive coupling between varying voltage sources and the signal lines.
Imaging a very low value air capacitor, (less than 1pf) connected between a varying voltage source and your signal line.
http://www.vtiinstruments.com/SupportBx4Qans.aspx?FaqID=115

 

[sophiecentaur]

I started an electrical engineering degree this semester. My book says that electrostatic noise meaningfully affects analog but not digital. But it does not say what electrostatic noise is, and neither Google nor Wikipedia readily yield an answer to this question: What is electrostatic noise?

This doesn't tell us the context of the noise. I read it as referring to what they often call 'static' interference on radio receivers. It's rather a vague term afaiac. 'Static' noise is not the familiar 'white noise' hiss but tends to consist of random impulsive spikes. It is caused by lightning, car ignition sparks, motors etc. and can be very noticeable.

The difference between digital and analogue signals is that an analogue receiver just detects the amplitude (or frequency) of the received carrier wave and presents this as a varying voltage to the loudspeaker. It cannot distinguish between wanted program or splats and noise so they are audible on the output. A transmitted digital signal is 'expected' by the receiver, to have certain values (perhaps just 0 or 1 - but most broadcast digital signals use more levels). If the noise / splats are below a certain level then the receiver can just ignore them because it correctly decides which value was intended and it can convert the digital information to exactly the same as what went in at the transmitter / studio. A decent digital transmission system can cope with occasional high spikes by using error-correction but it will eventually 'die' at a high enough interference level and the receiver mutes. Under the same conditions, a conventional analogue receiver may well operate still but with a disturbing level of background noise - it 'dies gracefully' so it may, in fact be better in some circumstances (comms rather than entertainment).