PhoneLabs starter kit

A few weeks ago, I received a package from the other side of the planet:

So, the folks at PhoneLabs sent me one of their Starter Kits to play with. This is a set of 3D printed parts along with some skrews and a rod that are designed to assemble into a simple setup for smartphone experiments.

The only thing that you need to add (besides your smartphone) is a ruler. Unfortunately, all rulers I tried were either too wide or too short, so I had to resort to a folding rule, which is not ideal because of the bulky folded part on one side, but still worked quite nicely.

As you can see from the video, I decided to try out our centripetal acceleration experiment and used our remote access to view the data on a laptop PC while rotating the phone. If you don’t know this experiment, here is the video, explaining the setup using a salad spinner:

The advantage of the 3D-printed setup over the salad spinner is, that you can vary the radius of your motion. I simply did the experiment three times in a row for different radii, pausing and resuming my measurement in-between. Here is the result (screenshot from the remote interface) after three repetitions:

You can clearly see and compare the three slopes, following a_{\mathrm{c}}=r\omega^2 nicely.

By the way, PhoneLabs also offer their own apps. While these do not provide features like remote access, there is something quite unusual and novel about them as you do not need to be installed anything on your phone. In fact, they simply run in your web browser from where they can still access some of your phone’s sensors.

Workshop in Aachen and update on upcoming events

Since this is the English version of this article, I should probably start with an update on international events. After really enjoying the AAPT Summer Meeting in Cincinnati (that’s where the image above comes from), I intend to attend the AAPT Winter Meeting as well, which will be in San Diego, 6-9 January. I still have to submit abstracts and book flights, so this will be fixed and officially announced later this year.

There will also be a big workshop in Aachen on academic teaching with phyphox. If you are a college or university educator near Germany, this will be the event for you. However, it will be held in German and you will find more information here.

Additionally, there will be more events to be announced for Germany this year and next year. There are at least four public events, which are fixed and a few more planned, but I am waiting for the official release and/or schedule from the organizer.

The future of phyphox

Don’t worry, we are here to stay and I’d just like to communicate a few plans for the near future and address some details, which might confuse those who follow us closely. If you are just interested in being able to use phyphox as a free app, do not worry – everything is fine. If you are interested in some details, the team and our plans, read on…

The team

First of all, let’s start with the change that might be confusing if not explained: I just got married and took the name of my wife. So, “Sebastian Kuhlen” is now “Sebastian Staacks”, but it’s still me and it is only a personal change for me, but absolutely no difference for phyphox.

Besides that, we are about to receive some help from our IT center and a new PhD student near the end of the year. While so far most of the development was done by myself (except for the much appreciated help from Jonas, a student who did a huge part of the iOS development at the beginning), there will be a software developer in training who will help for a few months and a PhD student, both working on a specific aspect of the app. Also, it is about time, that I update the “behind phyphox” section on the front page to also include those on the didactics front who have been there for a while now.


There will be even more help from people outside the RWTH Aachen University as many volunteered to translate phyphox at the GIREP conference in Dublin two weeks ago. If you want to translate phyphox to your language as well, I would be happy if you contact me. There are some requirements, though: First of all, be warned that there may be more text to be translated than you might expect and that just figuring out the right context may be more complicated than you might think. Also, you should be fluent in the language (ideally it is your first language) and you need to be a physicist in order to know the appropriate terms. Additionally, we require that you are a teacher at a school or university, so we can verify that you have a professional interest in translating. Finally, please be prepared on follow-up translations when new versions of phyphox introduce new text – this will not be much text and it will not occur too often, but it would be bad if we released new features and could not provide them in a language that we were able to provide before.

So, if you fulfill these requirements and I did not just scare you off, please contact me via the email address at the bottom of the page.

Open source

I have been promising this for a while now and as it happens so often, it took longer than expected. We intend to release the source code with the next major update (phyphox 1.1.0) or maybe its beta phase, so at that point anybody can contribute to its development. We just need to learn to develop the app as a team now and do not want to add to the confusion at this very moment.

Speaking of phyphox 1.1.0…

Upcoming features

Another thing I have been promising for a while is better graphs, which should be included in phyphox 1.1.0 in a few months. Those graphs are still far from being ready, but here is a little teaser to prove, that I am working on it:

The other major features for the upcoming version will be Bluetooth support and a much more convenient way to transfer custom experiments from our editor to the app. However, development on this has not yet started, so I am a little hesitant to promise too much at this point – you will certainly hear about it, when things start to take shape.

Version 1.0.8 (minor bugfixes)

We have just released a minor update with a handfull of bugfixes, especially addressing problems with the audio oscilloscope giving wrong data. In contrast to our regular updates, we push this one out on both systems as soon as possible since no features have been changed or added. Therefore the Android version should be available right now while the iOS version has to wait for Apple’s review process and is expected to be released until Friday.

Full Changelog

Changes for both Android and iOS

  • Fix wrong time axis of audio scope.
  • Allow unusual frequencies in tone generator but add a warning.
  • Rename centrifugal acceleration to centripetal.

Changes for Android

  • Fix OK-button not accessible on startup (small screens with enlarged fonts)
  • Fix rare crash in GPS module
  • Combine wrong GPS status to “deactivated/active”

Changes for iOS

  • Fix flickering of audio scope.
  • Fix crash on audio playback, mostly on iOS11.

Doppler effect experiments

A few weeks ago, two students from the University of Salzburg have started to create short videos in which they present various experiments demonstrating the Doppler effect.

Lukas and Thomas from the University of Salzburg

These videos will be presented by the Christian Doppler Fonds on and range from simple setups you can try at home to more involved ones which are well-suited for science classes in school. – and we are delighted that three of them use phyphox to determine the frequency shift using the Doppler experiment included in phyphox, which also calculates the corresponding velocity right away.

Unfortunately, these videos are only available in German, but if you are familiar with the Doppler effect, you should be able to easily follow their experimental setup just from the images. Here are the experiments using phyphox:

Magnetic Field of a Current Loop

The web form to collect the data (as part of an online script).

I just had a look at the data of our latest experiment assignment for our students. Just like in our previous collective measurement of pendulum frequencies, the students were supposed to submit their results through an online form, so we can combine all the data to test a model that will be discussed in an upcoming lecture. This time, they should measure the magnetic field generated by a current loop.

Since we could not expect that every student has got an adjustable current available, we instructed them to simply use an AA battery (non rechargeable, non Lithium, etc. for safety reasons) and connect it to any cable (like the USB cable in the picture above). After finding the location of the magnetometer in their phones, they simply should create a loop with the magnetometer in its center and measure the change in the magnetic field perpendicular to this loop. Repeat five times with varying radius and submit the results:

Since we do not know the actual current used in this experiment (at 1.5V this still depends on the cable and the battery’s internal resistance), we told them to include one measurement at a radius of 5cm and plotted the ratio B(r)/B(5cm) of the B field at any radius to the one at 5cm, to eliminate this unknown. Also, the plot only shows the absolute value as some students submitted negative changes.

I am quite satisfied with the results and am looking forward to the lecture in which we can presented the collective data to the students.

100.000 installs!

Woohoo, we have reached 100.000 installs (combined, Android and iOS) in less than a year. This is so amazing, thanks to you all! Please help us spread the word about phyphox even further by sharing your favorite experiment, a tweet/post/youtube video or just a link to our site with friends and colleagues – on the web or face-to-face.

Thanks again, to all of you!

Version 1.0.7 (GPS, saving of experiment states, …)

While we are already working on the big stuff like zoomable graphs, we decided to release yet another minor update in-between with some interesting features.

Full Changelog

And again, the full changelog for those who want to know every little detail or those who don’t like videos…

Changes for both Android and iOS

  • Save or share and load experiment states including your recorded data – even across platforms.
  • GPS support.
  • Audio autocorrelation and spectrum show corresponding musical notes.
  • You can now pick between different number of samples in audio spectrum.
  • New experiments: Accelerometer and magnetometer spectrum.
  • Time period of audio scope is now selectable.
  • Improved algorithm for audio autocorrelation.
  • Audio amplitude can now be calibrated to give sound pressure level in dB.
  • Splash screen with university logo.
  • Show magnetometer accuracy.
  • Move clear function to the action bar as a button.
  • Minor improvements to TalkBack / VoiceOver by adding descriptions to unlabeled buttons.
  • Buffer for acoustic stopwatch and inelastic collision has been increased, which might help on slower phones.

Changes for Android

  • Fix crash on Android 7.1 and Android O when reading non-3D sensors (like pressure or light).
  • Fix crash when rotating while the description hint starts showing.
  • Fix crash on bad experiment icons in main menu.

Changes for iOS

  • Fix crash on consecutive Fourier transforms.
  • Code has been converted to Swift 3. Ideally, there should be no noticable change. Ideally.
  • Old, discontinued audio engine has been replaced.
  • Fix: VoiceOver stopped working when phyphox handled audio.
  • University logo added to credits dialog.

File format update to version 1.5

  • Allow initializing buffers using a list of values.
  • Add mapping of ranges to value element to show text instead of numbers.
  • Add accuracy channel to sensors (magnetometer only).
  • Allow for dynamic sleep times of analysis cycles.
  • New analysis modules: round and log.
  • Fix handling of start value in subrange module.
  • Fix on Android: FFT module now uses actual number of data points instead of just the buffer size.
  • Fix on iOS: Button elements could not use buffers as inputs.

The editor and Wiki entries will be updated over the next few hours.