Time Domain ElectroMagnetic (TDEM) R&D project

[Doug2]

This is a document reporting about the design and tests of the prototype of a High power TDEM transmitter from Zonge with the funding of SERDP (dated 2003).

Very clever use of SCR's to generate high power, narrow half-cosine pulses.
I have looked on the web and I do not see this technology re-appearing anywhere in commercial systems but that could have been integrated in high-end instruments since then (2003).

That will be the base of our first prototype as we were seduced by the principles.

Willy

A US patented TDEM system using 1/2 sine pulses
Abstract
In a time domain electromagnetic mapping technique of the type using transmitter pulses of half-sinusoidal waveform, with the half sinusoids being segments of a sinusoidal waveform having a frequency and corresponding to a resonant frequency of the transmitter coil, an improved current fall time at the end of each pulse is obtained by forming each transmitter pulse of plural immediately successive half sinusoids, the transmitter coil being tuned to an appropriately increased resonant frequency relative to the pulse repetition rate. Circuits for generating the improved pulse waveforms are disclosed.


http://patentimages.storage.googleap.../US5796253.pdf

[Doug2]

This may be of interest as well
Sub-Audio Magnetics
http://www.gapgeo.com/divisions/gap-...dio-magnetics/
http://www.gapgeo.com/media/12455/gga_sam_ebrochure.pdf

[Willy Bayot]

A US patented TDEM system using 1/2 sine pulses
Abstract
In a time domain electromagnetic mapping technique of the type using transmitter pulses of half-sinusoidal waveform, with the half sinusoids being segments of a sinusoidal waveform having a frequency and corresponding to a resonant frequency of the transmitter coil, an improved current fall time at the end of each pulse is obtained by forming each transmitter pulse of plural immediately successive half sinusoids, the transmitter coil being tuned to an appropriately increased resonant frequency relative to the pulse repetition rate. Circuits for generating the improved pulse waveforms are disclosed.


http://patentimages.storage.googleap.../US5796253.pdf

Thanks.

This old patent improves the standard single bipolar pulse generation by generating a series of successive pulses in order to make profit of the resonant system and enlarge the total width of the transmitting pulse in practice.
Good idea!
Note that it is already using Thyristor switches (SCR's) back in 1998

Willy

[Willy Bayot]

This is the link to one interesting thesis from Canada (only for those who can read French)
http://www.ruor.uottawa.ca/fr/bitstr...pdf?sequence=3
Each bipolar pulse has a peak current of 700 Amp, a width of 486µsec and a pulse period of 16.6 msec to make a full period of 33.3 msec or 30 Hz. This is set for the regions where the power lines are at 60 Hz. In Europe, the pulse rate would be 25 Hz. By subtracting the decay voltages of a negative pulse from the previous positive pulse, the AC Power line effects are minimized.
Although it is not explicitly defined in the document, I think the switching was made by a H-bridge of SCR's and a resonant circuit with a low-ESR capacitor tuned to set this pulse width.


By the way, I am happy to see that the discussion machine has started ticking

Willy

[Orbit]

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to je to !

[Aziz]

62 72 6F 6A 20 31 20 69 6D 61 6D 6F 20 70 72 69 6D 61 72 6E 69 20 6B 61 6C 65 6D 20 75 20 6E 6A 65 67 6F 76 6F 6D 20 73 72 65 64 69 73 74 75 20 6A 65 20 20 62 72 6F 6A 20 32 20 73 65 6B 75 6E 64 61 72 6E 69 20 6B 61 6C 65 6D 20 6B 6F 6A 69 20 69 67 6E 6F 72 69 73 65 20 6D 61 67 6E 65 74 6E 6F 20 70 6F 6C 6A 65 20 70 72 69 6D 61 72 6E 6F 67 20 6B 61 6C 65 6D 61 20 70 72 69 6D 61 72 6E 69 20 6B 61 6C 65 6D 20 6A 65 20 70 72 69 6A 65 6D 6E 69 20 6B 61 6C 65 6D 20 6D 61 67 6E 65 74 6F 6D 65 74 72 61 20 69 74 64 20 64 61 20 6E 65 20 62 75 64 65 6D 20 64 6F 73 61 64 61 6E 20 64 65 63 69 6D 61 6C 61 6D 61 20 6E 6F 20 70 6F 65 6E 74 61 20 6A 65 20 76 69 73 65 6B 61 6E 61 6C 6E 69 20 70 72 69 6A 65 6D 20 62 65 7A 20 74 6F 67 61 20 6E 69 73 74 61 20 6F 64 20 6F 76 6F 67 61 20 67 6F 72 65
to je to !

broj 1 imamo primarni kalem u njegovom sredistu je broj 2 sekundarni kalem koji ignorise magnetno polje primarnog kalema primarni kalem je prijemni kalem magnetometra itd da ne budem dosadan decimalama no poenta je visekanalni prijem bez toga nista od ovoga gore

http://www.unit-conversion.info/text...adecimal/#data

[Qiaozhi]

broj 1 imamo primarni kalem u njegovom sredistu je broj 2 sekundarni kalem koji ignorise magnetno polje primarnog kalema primarni kalem je prijemni kalem magnetometra itd da ne budem dosadan decimalama no poenta je visekanalni prijem bez toga nista od ovoga gore

http://www.unit-conversion.info/text...adecimal/#data

Please write in English.

[Aziz]

Please write in English.

Good try. If I could.. *LOL*
No, I just have "cracked" the encoded message.
^sif

[Orbit]

poenata more channel receiving finally outputs channel after gain should not be added together but each of them are shown be displayed on the LCD or in software which works by each channel or final outcome divided into at least four for example, up to 6 or more sequences this approach allows that objects are actually visible very very It can be seen form size etc.sorry If not reasonably this is due to ....

[Orbit]

Share




the human eye the number of small parts if our brains analyzed image only partally eye and before that



it was divided into many parts they would see only a small part of the picture
in our visual field !

[Willy Bayot]

TDEM project update

Just a small update.
I have found an active partner on this R&D project. Together, we have made a number of LTSPICE simulations to check the validity of our design and timings.
We have now setup a first table-top prototype of the TDEM system delivering good-looking signals and decay curves with reduced voltage and currents.
The timing generator, signal processing and data storage firmware (running on an ARM LPC2148 from NXP) is ready to be tested on a prototyping board
See the two pictures attached.


Willy

[Geophyz]

Hi Willy,
this project is very interesting. If I understand the thread correctly you are interested in the differential TDEM as proposed in the SERDP funded work of Foley. I would like to also bring you attention to the work of French researchers who have built a machine with multiple time gate and exploited the viscosity effects on a man portable slingram TDEM for archaeological survey.
"Thiesson, J., Tabbagh, A. and Flageul, S.,
2007. TDEM magnetic viscosity prospecting using slingram coil configuration. Near Surface Geophysics. 5-6: 363-374."