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:

The last official drivers for the HP ScanJet 6300c from HP are only for Windows XP:

  ScanJet 6300c/cse/cxi/6350c/cse/cxi/6390c PrecisionScan Pro software/driver - SCSI and USB            Windows XP    95.27M    
  ScanJet 6300C/6350C/6390C series PrecisionScan Pro driver update and button fix - USB and SCSI    Windows XP    487.5k

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 modified Nikon D70 was measured:



In addition to the 436 nm and 404 nm lines of the visible Hg spectrum, the 365 nm line of the Hg spectrum and two new UV lines in red (false colour) are clearly visible.

Due to the small sensor of the camera, only three lines of the Hg spectrum are visible at the screen of the camera.
Two of them are in the visible part of the spectrum, the third line is in the UV, 365nm, and is visible as a red line. This red is a false colour.

Here is the experimental setup:



At the right hand side you can see the Nikon D70 without a camera lens.
The other camera Canon 10 D is recording spectra from the UV screen.

Complete Hg spectrum:

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.