thermal noise

A

Allan Adler

Guest
How does one measure thermal noise in a resistor?

Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu

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* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
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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.

--

Greetings,

Jerry Greenberg GLG Technologies GLG
=========================================
WebPage http://www.zoom-one.com
Electronics http://www.zoom-one.com/electron.htm
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"Allan Adler" <ara@nestle.ai.mit.edu> wrote in message
news:y93brs9c66x.fsf@nestle.ai.mit.edu...

How does one measure thermal noise in a resistor?

Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu

****************************************************************************
* *
* Disclaimer: I am a guest and *not* a member of the MIT Artificial *
* Intelligence Lab. My actions and comments do not reflect *
* in any way on MIT. Moreover, I am nowhere near the Boston *
* metropolitan area. *
* *
****************************************************************************
 
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 - http://home.cfl.rr.com/aichip
 
Allan Adler <ara@nestle.ai.mit.edu> wrote:

: How does one measure thermal noise in a resistor?

: Ignorantly,

Connect to an RMS voltmeter at much lower temperature
--
Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------
 
Allan Adler <ara@nestle.ai.mit.edu> wrote:

: 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
--
Uwe Bonnes bon@elektron.ikp.physik.tu-darmstadt.de

Institut fuer Kernphysik Schlossgartenstrasse 9 64289 Darmstadt
--------- Tel. 06151 162516 -------- Fax. 06151 164321 ----------
 
This page has notes on how to do the experiment (scroll down to the
subheading "Experiment" on page 3)

http://www.physics.utoronto.ca/undergraduate/PHY_225H_280F-281S/experiments/
thermal-noise/Thermal-Noise.pdf

(Long URL may wrap and need repairing)

Colin


"Allan Adler" <ara@nestle.ai.mit.edu> wrote in message
news:y93brs9c66x.fsf@nestle.ai.mit.edu...
How does one measure thermal noise in a resistor?

Ignorantly,
Allan Adler
ara@zurich.ai.mit.edu


****************************************************************************
*
*
* Disclaimer: I am a guest and *not* a member of the MIT Artificial
*
* Intelligence Lab. My actions and comments do not reflect
*
* in any way on MIT. Moreover, I am nowhere near the Boston
*
* metropolitan area.
*
*
*

****************************************************************************
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