Huygens Optics | Metal Detector Discrimination Explained (with a Garret AT Pro) @HuygensOptics | Uploaded November 2019 | Updated October 2024, 1 hour ago.
In this video I discuss the principle of a VLF- type induction balanced metal detector (Garrett AT pro), in particular how the discrimination between different metals works. I do this by looking at the emitted and received signals of a test coil, so not by opening up the detector.

00:00 General Intro
00:34 Need for discrimination / ID in metal detection
03:19 Test setup
03:55 Principle of double D coil explained
08:29 ID and phase shift for different metals (para- and diamagnetism)

It turns out that the detector measures the phase delay between the emission and reception coil. The reception coil shows this delay because of changes in the inductance which are introduced by the conductivity and intrinsic magnetic properties of metal objects in the vicinity.

$Coherence part 3: This is not a wave. Trying to find analogies between the wave energy confined in a string and matter interacting with light. 0:00 Intro 6:38 Experiments with waves in a string 15:40 Analogies with electron behaving as waves 22:50 Changing the standing wave mode in a string using phase manipulation 26:49 A hypothetical model for demonstrating quantized wave behavior in a string 32:26 Elastic-Inertial Poetry For this video I used a a few short clips from the following videos and websites: Spinning ball (from Mike Shake): https://www.youtube.com/watch?v=mNBEyjE72w8 Charged ball (from Plasma Channel) https://www.youtube.com/watch?v=nxagMrTVonQ Refracted wave: (by Ulflund) https://commons.wikimedia.org/w/index.php?curid=73784342 If you like the painting then visit the Rene Magritte website: https://www.renemagritte.org/the-treachery-of-images.jsp Wave animation at 32:25 by Nils Berglund: https://www.youtube.com/@NilsBerglund Did I forget anybody? let me know an I will set it straight.$

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$Directional coherent wave source This short shows a directional wave source that is made by spacing omnidirectional wave emitters in a very specific configuration. The animations were created using the wave simulation code made by @DiffractionLimited As for the question at the end of the video about being able to spot how destructive interference comes about: this is basically impossible to see in the animation. So the answer to the question is NO. However, there are few ways that you can look at how the phenomenon comes about: 1) When moving away in the horizontal direction of a row of emitters, for every point there is an equal amount of emitters that has a particular phase, compared to the emitters that have a phase 180 degrees shifted. So, when adding up these 2 contributions for all the emitters together in a row, this results in a wave amplitude that is almost zero in this direction. 2) An alternative way to look at this is the following: because of the spatial separation of exactly 1 lambda in the vertical direction, a standing wave arises in the array that has almost equal field strength in the horizontal direction within the array. And because the sources are moving in phase with the standing wave, they cannot transfer energy into the surrounding field in the horizontal direction. This also explains why a low intensity in the horizontal direction exists. Both views are in my opinion valid, but I think the second one is a bit more intuitive. Simulation code supplied by @DiffractionLimited The image files for the simulation can be downloaded here: https://huygensoptics.com/2D_wave_sims/coherent_source_detail.png https://huygensoptics.com/2D_wave_sims/coherent_emitter_vertical_100.png #light #physics #optics #short$

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$Coherence in star light This short discusses (very briefly) the difference between temporal and spatial incoherence. It also contains a wave animation of a telescope mirror that concentrates a field on a sensor. Of those of you who want to know more about coherence I made these videos: Temporal coherence: https://www.youtube.com/watch?v=dtcq5b0R65w Spatial coherence: https://www.youtube.com/watch?v=nba4ztLBEh0 Presented here are 2D-animations of a field, which means that the intensity of the focused light at the sensor increases with the diameter of the mirror. In a 3D scenario however, the intensity increases with the square of the diameter of the mirror, leading to a much larger difference between the incoming and focused radiation intensity. Simulations were created using the python code supplied by @DiffractionLimited The simulation image file can be downloaded from: https://huygensoptics.com/2D_wave_sims/telescope_incoherent_light.png Milky Way picture by Philippe Donn #short #light #physics #optics$

Metal Detector Discrimination Explained (with a Garret AT Pro) @HuygensOptics