Using a condenser microphone and the FFT HP3561A analyzer, a 200 Hz square wave signal was fed into an ESL (Martin Logan Sequel II electrostatic loudspeaker):



This is the electrostatic speaker:


FT signal of the 200 Hz square wave of the function generator:


FT signal of the condenser measuring microphone:

Hello Tesla friends

I have two questions:
1. Has anyone done an electromagnetic spectral analysis of Tesla coils in operation?
2. Has anyone determined the self-resonances of Tesla coils in the off state, perhaps with shorted spark gaps?

Just before Christmas, two atmospheric Tesla discharges:

The magnetic flux density was measured at the surface of permanent disc magnets by a Hall probe:

Disc magnet 30mm diameter, height 15 mm, NdFeB:




Results:

Disc center 0.44 T
1 cm distance 0.2 T
2 cm distance 0.06 T
Edge up to 0.5 T
Side part of the disc (curved) 0.06 T

Disc magnet 45 mm diameter, height 30 mm, NdFeB:




Results:

Disc center 0.52 T
1 cm distance 0.28 T
2 cm distance 0.14 T
edge up to 0.6 T
side part of the disc (curved) 0.06 T

The picture shows an electrostatic voltmeter with light mark pointer for a maximum of 30 kV.



In contrast to the other 10 kV electrometer, this instrument has two additional measuring ranges 7.5 kV and 15 kV:

Under Windows 10, the HP Scanjet 6300c worked without problems.
After an automatic update to a new version of Windows 10, the scanner stopped working.
Despite much work, I could not use the scanner anymore.
Please, does anyone have any advice?

regards

Physikfan

The UV sensitivity of a Nikon D70 was measured by using a Hg spectrum. The camera was used without a camera lens in an open spectrometer configuration, consisting of a quartz lens, a reflection grating and a Hg high pressure lamp as a light source:



In addition to the 436 nm and 404 nm lines of the Hg spectrum, the 365 nm line of the Hg spectrum in red is clearly visible.

The spectra are photos of Hg spectra with constant exposure time, light source is a Hg high-pressure lamp, the entrance slit is imaged with a quartz lens via a reflection grating on a screen, to detect the UV lines, the left part of the screen is coated with an ultraviolet luminous color.

The first picture is the Hg reference spectrum, the lines go deep into the UV.


The second picture shows the Hg spectrum, filtered by cheap sunglasses.
The color of the blue line in the spectrum of the sunglasses also corresponds to the color of the visual impression with unarmed eye.
The color of the violet line in the Hg reflectance spectrum does NOT match the color of the visual impression with unarmed eye, and is an artifact, probably due to overexposure at this point.
To my surprise, the quality of the sunglasses is excellent in terms of UV protection,
I will now use these glasses as goggles for my further UV experiments.
UV experiments with normal glasses are in preparation.

To all friends of antique Geissler tubes

The picture shows a complex shaped Geissler tube.


Unfortunately, the corresponding metal cap with eyelet is missing during a contact.
Please, does anyone know how to fix this problem?

Best regards

Physikfan

Hello to all IT insiders

My question:

I currently have access to Internet boxes different providers at the same location.
How can I reasonably objectively check the Mbit rates of different providers?

Please the answers in understandable language for non-professionals in digital electronics!!!

Best regards

Physikfan

The two pictures show a beetle in a Geißler tube:
(DC source, 9 kV, cathode top, anode bottom)



Exposure normal, with room lighting, fluorescence on the glass wall


Exposure 2 f-stops underexposed, room dark, fluorescence on the glass wall


Exposure 2 f-stops underexposed, room dark