Noise and Interference basics (Raymond Schouten) txtpage1
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    	              INTRODUCTION:

	Usual statement: All signals I don't want = NOISE

	It's better to discriminate between:
	INTERFERENCE: "man-made"
	NOISE       : "nature-made"

	Interference level is set by environment, wiring and 
	shielding. Usualy specific frequency components are 
	introduced.

	Noise level is set by the used source-sample-amplifier-
	temperature combination. The expected level can be 
	calculated from this.
	Noise contains no specific spectral components. 

	The lowest measurement limit is set by the noisefloor,
	the practicle limit can be higher caused by 
	interference.


		   INTERFERENCE SUBDIVISIONS:

-Thermal drift     d.c. up to 10Hz thermoelectric voltages, air flow 
		   etc.
			
-Mechanical        d.c. up to 1kHz causing electrical effects like 
 vibrations        charge displacement. (Also: near 50Hz from motor)  

-Hum               50-100-150Hz ("sine/square") in sync with power line

-Line switching	   Short spikes in sync with line (from power control
                   circuits) or random occurring from on/off switching.

-Radio Frequency   Signals from 200kHz up generated in signal wires
 signals (RF)      (forming antennes). Causing low frequency-signals 
                   on nonlinear circuits (PN-junctions) 

-System            In setups with high gain amplifiers, poor grounding 
 oscillations      or shielding, unwanted positive feedback can cause 
                   sudden oscillations.


		   NOISE SUBDIVISIONS :

-Drift,aging       Slow (<0.1Hz) changes in electronic parameters
			
-1/F noise         Noise (voltage,current) generated in electronics
                   with a rising level at lower frequencies (<100Hz)
                   can be confused with thermal or mechanical
                   interference. With electronics, sometimes 0,1...10Hz 
		   (peak-peak) noise level is specified to give an
		   indication. With preamplifiers spotnoise at 1Hz 
		   (or at 10Hz) is usually specified (Vrms).

-White noise       Noise (voltage,current) showing a flat frequency 
                   spectrum, generated in electronics, resistors and
                   other dissipative elements.(Keywords:thermal noise,
  	           shot noise).