Quick question about the F70 "dirt" meter...

Trying to understand ground phase, and then the DEGREE of mineralization in the soil, I came across the following quote from Mr. Dankowski:

"Ground Balance numbers merely tell you the TYPE of ground....and NOT the AMOUNT of ground minerals. It is the Fe3O4 bar-graph that starts to show you the amount of mineralization........especially if it's magnetite."

Since the F70 does not have a Fe304 bar graph, is the "dirt" meter similar? Does it tell the same thing (amount of mineralization?) I'm assuming so, but when I see people refer to ".1 on the Fe3O4 meter" on F75/T2 machines, I don't know how this compares to my "dirt" meter readings...

Thanks,

Steve



Edited 1 time(s). Last edit at 02/12/2011 11:06AM by steveg.

Glad you brought this up......as I intended to clarify this .... quite a while ago.

Yes, the DIRT bar-graph on the F70 is a direct form of Fe3O4 magnetite.....and is to be used in the same fashion. Magnetic susceptibility gauge. I'm not sure why it was incorporated into the design of these detectors.........as most detectorists are not that technical.....and probably never pay mind to it; however, it is a critical indicie for us technically-minded folks.....many of which are on this forum. Magnetic susceptibility can completely kill the performance of VLF IB detectors.....which is nearly all of the ones on the market today.

.... This brings up ANOTHER like-subject. Magnetite is NOT the only type of mineralization in the ground that can affect the performance of electromagnetic metal detectors; however, it is the primary offender...........and is the reason for incorporating.....in bar-graph form.

What is interesting... is that a PI (Pulse Induction) detector......which is still a electromagnetic detection device.......under many circumstances.....can completely ignore magnetite........and still ascertain full depth capabilities. This is performed through a exacting time delay of WHEN to turn the receiver back on......(after the transmitter is turned off)......and analyze 'return' EMF. The 'decay' rate of magnetite is completely different.......as compared to solid metal objects. When you 'energize' ..... 'light-up'.... the ground with EMF (from a external source....the metal detector)......ground mineralization usually decays (ramps down) at a faster rate....as compared to actual diamagnetic, paramagnetic, ferromagnetic metal targets.

Thanks for clarifying about the dirt meter.

And, thanks for the additional info on a PI machine. Your description there is FASCINATING. What a cool thing! You know, there are alot of parallels, it is seeming to me, between weather radar theory, and metal detector theory. Both use transmitted electromagnetic radiation to find "targets," which they find by sensing tiny returns back to the receive mechanism -- and then indicating these "returns" as "targets." Doppler radar, then, was an advance that was developed, in which not only could you measure electromagnetic RETURN (thus "seeing" a raindrop), but you could also measure the PHASE SHIFT which a moving raindrop imparts on the electromagnetic pulse. Measuring this "phase shift" with the receive equipment, then allows you to ascertain not only the LOCATION of a raindrop, but now the DIRECTION OF MOTION of the raindrop (and thus being able to see "rotation" in a supercell thunderstorm -- an huge advance in tornado forecasting!) This breakthrough happened through engineers who were used to dealing with properties of electromagnetic radiation, and really thinking about how to make best use of the properties of electromagnetism in this application. Seems like the very same thing happens with engineers and metal detecting. I see this whole "decay rate" of magnetite being different than the decay rate of a "good" target when being illuminated with electromagnetism and then being used to "eliminate" the effects of magnetite, as being very similar to the "Doppler" breakthrough w.r.t. weather radar.

COOL STUFF, thanks for sharing!

Steve

Very exacting!