Research Techniques - Characterizing and avoiding noise and interference in instrumentation

# Research Techniques - Characterizing and avoiding noise and interference in instrumentation [TOC] ## Competences See https://docs.google.com/spreadsheets/d/17e31WqewXqjbbJ431B478XNPCzT_eZEuUy9-ah5XhkI (outdated). ## Learning Goals See https://docs.google.com/document/d/1jovFc98XYRqvoKjY-H3Hfnllcskz8cUs58a_H2c8e0I/ (outdated). ## Learning Tasks :::info **Estimated time (for complete unit)**: * Self-learning: ≤180 minutes * Practical sessions: 240 minutes **Learning Goals (for complete unit)**: * You are able to use complex impedances to compute the behavior of electric networks with resistances, capacitances and inductances. * You are able to estimate parameters for wiring and other components. * You understand the mathematical background of spectral estimation. * You have a basic understanding of possible software implementations of spectral estimation using time-series data. * You are able to use the general-purpose Hangleiter tool for spectrum acquisition  * You have an understanding of the most common electrical noise sources. * You are able to differentiate between electrical noise sources in the spectrum. * You are aware of the concept and sources of EMI/microphonics. * You are able to recognize the most prominent features in a noise spectrum (e.g. 50 Hz Peaks). * You are aware of less common interference sources. (e.g. acoustic noise modes). * You are able to use built-in (software) spectrum analysis options of general purpose data acquisition tools. * You are able to configure hardware and software parameters for spectrum acquisition according to your needs and without further guidance. You are aware of common pitfalls such as aliasing or a badly chosen windowing function. ::: ### 0. Prerequisites :::info **Estimated time**: ≤45 Minutes **Learning goals**: 1. You are able to use complex impedances to compute the behavior of electric networks with resistances, capacitances and inductances. 2. You are able to estimate parameters for wiring and other components. ::: In order to follow the course, you should be familiar with complex impedances and the wave-description of electrical signals. - [ ] Read or watch [chapter 2](https://moodle.rwth-aachen.de/pluginfile.php/2446824/mod_folder/content/0/Ch2_impedance.pdf) / [lecture 3](https://moodle.rwth-aachen.de/pluginfile.php/2446824/mod_folder/content/0/L3_10-05-2021.mp4) (31:00 min -) of the RF lecture to brush up your knowledge of and familiarize yourself with complex impedances.  ### 1. Spectrum Acquisition :::info **Estimated time**: 20 Minutes for Section 1.1 - Mathematical Background, 35 Minutes for Section 1.2 - Software implementations, 35 Minutes for Section 1.3 - Noise characterization, 120 Minutes for Section 1.4 - Data Aquisition (Practical Session), ::: The most efficient way of estimating a power spectral density is Welch's method. In this section you will get a basic idea of how the method works, how it can be implemented in software before moving on to acquire noise spectra on a real instrument to familiarize yourself with the effects and interplay of different parameters. Finally, you will investigate the influences of different cables and loads connected to the input of a voltage meter. #### 1.1 Mathematical Background :::info **Estimated time**: 20 Minutes **Learning goals**: 1. You understand the mathematical background of spectral estimation. ::: - [ ] Watch the [lecture video L8](https://moodle.rwth-aachen.de/pluginfile.php/2446824/mod_folder/content/0/L8_14-06-2021.mp4) (35:30 min - 45:45 min) and/or read [chapter 5.7](https://moodle.rwth-aachen.de/pluginfile.php/2453685/mod_folder/content/0/2022-06-17%20-%20Hangleiter%20-%20Noise%20characterization%20workshop.pptx). - [ ] Read [these seminar talk slides](https://moodle.rwth-aachen.de/pluginfile.php/2453685/mod_folder/content/0/2022-06-17%20-%20Hangleiter%20-%20Noise%20characterization%20workshop.pptx). - [ ] For those interested, the [original paper](https://ieeexplore.ieee.org/document/1161901) is a good read, but not required. - [ ] Answer the following questions: 1. How do you translate your time trace into a frequency spectrum?. 2. What are the advantages/disadvantages of "Windowing"?. #### 1.2 Software implementations :::info **Estimated time**: 35 Minutes **Learning goals**: <ol start="2"> <li>You have a basic understanding of possible software implementations of spectral estimation using time-series data. </li> <li>You are able to use the general-purpose Hangleiter tool for spectrum acquisition. </li> </ol> ::: - [ ] Read the documentation of the [`scipy.signal.welch` method]( https://docs.scipy.org/doc/scipy/reference/generated/scipy.signal.welch.html). - [ ] Read and understand the function of all input parametes. Write down which values you would select or where in the data aqusition process you can read out these values. - [ ] Implement and understand the code examples given in the documentation. - [ ] Download the spectrometer class package from [GitLab](https://git.rwth-aachen.de/qutech/qutil) and install it following the instructions in the `README.md` file. - [ ] Read the [documentation](https://qutech.pages.rwth-aachen.de/qutil/_autogen/qutil.measurement.spectrometer.html#module-qutil.measurement.spectrometer).   #### 1.3 Noise characterization :::info **Estimated time**: 35 Minutes **Learning goals**: <ol start="4"> <li>You have an understanding of the most common electrical noise sources. </li> <li>You are able to differentiate between electrical noise sources in the spectrum.</li> <li>You are aware of the concept and sources of EMI/microphonics.</li> <li>You are able to recognize the most prominent features in a noise spectrum (e.g. 50 Hz Peaks). </li> <li>You are aware of less common interference sources. (e.g. acoustic noise modes).</li> </ol> ::: - [ ] Read [chapter 7.0](https://moodle.rwth-aachen.de/pluginfile.php/2446824/mod_folder/content/0/Ch7_8_EMI_filtering.pdf) / watch [lecture 9](https://moodle.rwth-aachen.de/pluginfile.php/2446824/mod_folder/content/0/L9_17-06-2021.mp4) (38:00 min - 48:00 min) as well as [this article](https://www.eetimes.com/electrical-noise-and-mitigation-part-1-noise-definition-categories-and-measurement/) to familiarize yourself with the concept of EMI and possible sources thereof. - [ ] Watch this EEVblog video to learn how to track down common-mode noise: {%youtube BFLZm4LbzQU %}  #### 1.4 Data Aquisition (Practical Session) :::info **Estimated time**: 150 Minutes **Learning goals**: <ol start="9"> <li>You are able to use built-in (software) spectrum analysis options of general purpose data acquisition tools.</li> <li>You are able to configure hardware and software parameters for spectrum acquisition according to your needs and without further guidance. You are aware of common pitfalls such as aliasing or a badly chosen windowing function.</li> </ol> ::: Continue on with the [step-by-step instructions](https://iffmd.fz-juelich.de/PoGCsD_MSDi9bvmA7Z6RKw). ### 2. Noise mitigation #### Setting up a measurement system :::info In this session you will use the spectral estimation techniques from [section 1](#1-Spectrum-Acquisition) to systematically study how equipment and its connections influence setup noise, learning how to wire up and ground a measurement setup for typical solid-state device experiments, and which pitfalls to avoid. **Estimated time**: * Self-learning: 45 minutes * Practical session: 120 minutes :::spoiler **Learning Goals** 1. You will be able to develop and apply a wiring strategy to avoid interference. Practical sessions in the lab will illustrate different wiring settings. 2. <b></b> 2.1. You will be aware of best practices for setup grounding. 2.2. You will be able to implement a grounding strategy for a new setup and maintain good grounding practices for setup changes. 2.3. You will be able to quantitatively assess impact of, e.g., ground loops 3. You will be able to quantitatively estimate the impact of spectral features on signal-of-interest. Using the Hangleiter tool will give basic insight. 4. <b></b> 4.1. You will be aware of strategies to match observed noise features to setup components. 4.2. You will be able to devise a test for checking the noise source hypothesis. 4.3. You will be able to use the correct noise hunting technique for this check. 5. You will know about and be able to apply different strategies to systematically study the noise content of a setup. 6. You will be able to combine all previous learning goals to find flaws in a (purposefully) noisy setup. ::: ##### Preparation - [ ] Read [chapter 7.1-7.3](https://moodle.rwth-aachen.de/pluginfile.php/2446824/mod_folder/content/0/Ch7_8_EMI_filtering.pdf) / watch [lecture 9](https://moodle.rwth-aachen.de/pluginfile.php/2446824/mod_folder/content/0/L9_17-06-2021.mp4) (48:00 min -) to lecture 10 (- 18:00 min) to get a basic idea on how wiring affects a setup and what good strategies are - [ ] Read [this section of the NI blog](https://www.ni.com/en-us/support/documentation/supplemental/06/field-wiring-and-noise-considerations-for-analog-signals.html#section-1955790383) for a structured approach to noise hunting - [ ] Read [this blog post](https://neurogig.com/elementor-294/) for an extended discussion on noise hunting - [ ] Familiarize yourself with the [the Basel amplifier](https://www.baspi.ch/_files/ugd/68eb62_8d15cc98d11c4074ba2cbe94feef397d.pdf). - [ ] (optional) Read chapter 4 in the Morrison book #### Practical session Continue on with the [step-by-step instructions](https://iffmd.fz-juelich.de/gIrsInvRQte6SaJsr0NzvQ?both#Noise-mitigation).