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噪聲實(shí)驗(yàn)裝置

• 約翰遜噪聲，“布朗運(yùn)動(dòng)”的電子檢測和量化
• 演繹玻爾茲曼常數(shù)，K _乙，從約翰遜噪聲對(duì)溫度的依賴性
• 觀察散粒噪聲和量化，以衡量基本電荷ê '
• 用于多種測量的前端低一級(jí)的電路配置
• 調(diào)查的功率譜密度和電壓噪聲密度信號(hào)，他們的V / Hz和V /√Hz為單位
• 應(yīng)用傅立葉噪聲密度噪聲信號(hào)轉(zhuǎn)換成數(shù)字化處理的方法
• 探索放大，濾波的頻率，平方和平均時(shí)間
• 培養(yǎng)技能適用于整個(gè)測量科學(xué)的廣度

噪音基本裝置是一組工具，先進(jìn)的和中間的實(shí)驗(yàn)室教學(xué)和學(xué)習(xí)有關(guān)電子噪聲。在所有的電子信號(hào)中存在的噪聲限制了許多測量的靈敏度。這，本身將是足夠的理由來激勵(lì)學(xué)習(xí)如何可以量化噪聲。但是，電子噪音可以遠(yuǎn)遠(yuǎn)超過滋擾，或限制-蘭道爾的一句名言，有時(shí)噪音的信號(hào)“。事實(shí)上，至少有兩種情況，即噪聲的測量可以得到的基本常數(shù)。

通過集中處理和約翰遜噪聲和散粒噪聲測量，TeachSpin的噪聲基礎(chǔ)，讓學(xué)生以確定雙方玻爾茲曼常數(shù)，_K B ，電子電荷的幅度，' E '。

約翰遜噪聲的波動(dòng)電動(dòng)勢(shì)在任何**溫度Ţ > 0 ​​電阻油然而生。Nyquist的預(yù)測是，這個(gè)電動(dòng)勢(shì)的均方服從< V ²（t）的> = 4 K _BTR D F ，D F 噪聲測量帶寬。此結(jié)果使要測量的玻爾茲曼常數(shù) k _乙。

散粒噪聲是衡量觀察到的波動(dòng)一定的電流，由于量化地對(duì)它們所加的粒度。在這種情況下，肖特的預(yù)測是一個(gè)直流電流我_直流服從另一均方有關(guān)的波動(dòng)會(huì)伴隨著，[δ 我（噸）] ² > = 2 ë鍵我_直流 D F。此結(jié)果使要測量的基本電荷ë鍵的大小。

從這些來源之一，還有更多的噪音，可以觀察到，因?yàn)槟K化，用戶可配置的，我們的電子安排。本裝置的信號(hào)流的透明布局使得它很清楚如何在實(shí)踐中量化噪聲，由于過程的放大，濾波的頻率，平方和平均的時(shí)間，可以單獨(dú)和詳細(xì)理解。其結(jié)果是量化噪聲的方法，和噪聲密度，學(xué)生其實(shí)可以理解。這會(huì)產(chǎn)生一個(gè)便攜式的一套適用于整個(gè)測量科學(xué)的廣度技能。 噪聲測量在物理學(xué)的許多領(lǐng)域中有一個(gè)非常當(dāng)前的應(yīng)用程序。

Introduction

• Detect and quantify Johnson noise， the ‘Brownian motion’ of electrons
• Deduce Boltzmann’s constant， k_B， from the temperature dependence of Johnson Noise
• Observe and quantify shot noise in order to measure the fundamental charge ‘e’
• Configure front-end low-level electronics for a variety of measurements
• Investigate ‘power spectral density’ and ‘voltage noise density’ of signals， and their V²/Hz and V/√Hz units
• Apply Fourier methods to digitally process noise signals into noise densities
• Explore amplification， filtering-in-frequency， squaring， and averaging-in-time
• Develop skills applicable across the breadth of measurement science

TeachSpin's Noise Fundamentals is a set of tools for teaching and learning about electronic noise in the advanced and intermediate laboratory. The noise present in all electronic signals limits the sensitivity of many measurements. That， in itself， would be reason enough to motivate learning how noise can be quantified. But electronic noise can be much more than a nuisance， or a limit -- in the famous phrase of Landauer， sometimes ‘noise is the signal’. In fact， there are at least two cases in which the measurement of noise can give the values of fundamental constants.

By concentrating on the processing and measurement of Johnson noise and shot noise， TeachSpin’s Noise Fundamentals allows students to determine both Boltzmann’s constant， k_B， and the magnitude of the charge on the electron， ‘e’.

Johnson noise is the fluctuating emf which arises spontaneously in any resistor at absolute temperature T > 0. Nyquist’s prediction is that the mean square of this emf obeys < V²(t) > = 4 k_B T R Df， where Df is the bandwidth over which noise is measured. This result allows Boltzmann’s constant k_B to be measured.

Shot noise is a measure of the fluctuations observed in certain currents， due to the granularity imposed on them by the quantization of charge. In this case， Schott’s prediction is that a dc current i_dc will be accompanied by fluctuations obeying another mean-square relation， < [δi(t)]²> = 2e i_dc Df. This result allows the magnitude of the fundamental charge e to be measured.

Noise from either of these sources， and many more， can be observed because of the modular， and user-configurable， arrangement of our electronics. The transparent signal-flow layout of our apparatus makes it very clear how noise is quantified in practice， since the processes of amplification， filtering-in-frequency， squaring， and averaging-in-time can be understood separately and in detail. The result is a method for quantifying noise， and noise densities， that students can actually understand. This generates a portable set of skills applicable across the breadth of measurement science.