thermal noise

This is a complex answer. Noise must be compared to something, such as a standard. The noise in a component such as a resistor would be dependent on factors such as the temperature of the device, the current through the device, the applied voltage, the frequency of the voltage, waveform or structure of the applied voltage, and the humidity if the resistor is of a high enough value. These are only the simple attributes that I can think about at this time.

As for noise measurements, they are usually compared or scaled to some type of reference. You can measure the noise in simple volts, but this would be meaningless by way of definition unless you have a standard to compare it to. When publishing the noise factor, all the conditions of the test must also be specified.

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Jerry Greenberg GLG Technologies GLG ========================================= WebPage

How does one measure thermal noise in a resistor?

Ignorantly, Allan Adler snipped-for-privacy@zurich.ai.mit.edu

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Simple comparative means are to measure noise at a given temperature, then change the temperature and try again. Since the thermal noise power in Hertz is equal throughout the frequency spectrum, you only need to worry about the values of k and T where k is Boltzmann's constant, and T is the temperature of the conductor in Kelvins.

Cheers!

Chip Shults My robotics, space and CGI web page -

: How does one measure thermal noise in a resistor?

: Ignorantly,

Connect to an RMS voltmeter at much lower temperature

-- Uwe Bonnes snipped-for-privacy@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt

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: How does one measure thermal noise in a resistor?

: Ignorantly,

Connect to an RMS voltmeter with the voltmeter at much lower temperature and the resistor at nominal temperature.

Bye

This page has notes on how to do the experiment (scroll down to the subheading "Experiment" on page 3)

(Long URL may wrap and need repairing)

Colin