Recording Scheme
No Recipe
- How deep you want to go?
- What is the noise level?
- How conductive is the ground?
- How is the magnetic activity?
The only available recipe is: record as long as possible.
Hint
With a lowest recording frequency of 512 Hz for all systems you are always perfectly synchronized1.
ADU-11e lowest native frequency is 1024 Hz.
Scheme
| sampling rate | filter offline |
|---|---|
| 131072 Hz | (short) record |
| 65536 Hz | record |
| 16384 Hz | filter |
| 4096 Hz | record |
| 1024 Hz | record / filter |
| 256 Hz | filter |
| 64 Hz | filter |
| … tbc | filter |
So simply spoken: record two bands at the same time. Set the duration you want for 16 kHz, but record 64 kHz.
So instead of 3 min 64 kHz and 12 min 16 kHz, you record 12 min 64 kHz (sure you also can record 12 min 64 kHz with activated 4x filter).
Fluxgate
The recording time should be at least one week for periods greater than 10,000 s.
Considering that with induction coils you can measure down to 4096 s, and you purchased a fluxgate, the guess is that you are interested in periods greater than 10,000 s.
So 40,000 s to 100,000 s are needed to get significantly deeper: 3 weeks of recording time is needed.
SHFT
The SHFT-02e and SHFT-03e are used for AMT/CSAMT. Your recording time should be at least 1 - 5 min. You are depending strongly on the magnetic activity.
Coils
First of all be aware that frequencies above 1 kHz are difficult to get (see above). In countries like Brasil you can be lucky, in countries like Germany you may sad
How deep?
This is a question which can not been answered directly. Learn that please.
Question: How far do I get when I drive for one hour on a motorway?
Answer: depends on our speed (aka conductivity) and traffic jam (aka noise level).
… it sounds cruel … but you have to respect two parameters to answer one question.
| coil preferred | duration | application type | environment | periods | depth |
|---|---|---|---|---|---|
| MFS-12e | 1-2 days | general studies / geothermal | sediments | 1000s | 3-6 km |
| MFS-06e | 3-6 days | general studies | sediments | 5000s | 8-12 km |
| MFS-12e | 1-2 days | general studies | rocks | 1000s | 8-15 km |
| MFS-06e | 3-6 days | general studies | rocks | 5000s | 20-100 km |
| MFS-12e | 1-2 days | general studies / geothermal | sediments | 1000s | 3-6 km |
| MFS-12e | 1-2 days | general studies / geothermal | rocks | 1000s | 8-15 km |
| MFS-12e / 07e | 8 hours | general studies / geothermal | sediments | 100s | 2-3 km |
| MFS-12e / 07e | 8 hours | general studies / geothermal | rocks | 100s | 4-6 km |
| SHFT-02e / 03e | 15 mins | environmental | normal soils | 1 kHz | 30-100 m |
These values are for medium noise level.
For a target located in a quite area you can reduce the recording time by a factor of 2 -4.
However, if you make it too short, you have no chance to improve the results by changing parameters (statistics) - or for beginners: a “one stack recording” is always a “stack all” interpretation.
Footnotes
the 256 Hz synchronicity is subject of being removed in the future. It is only for working with ADU-07e systems together. ADU-08e and higher may have an optionally different 256 Hz sync. So take 512 Hz as the default for long term recording.↩︎