BarnacleBill
New member
In my junk box I have the fortune to have a couple of spare pieces of Ferrite that I use in various designs. Ferrite has been used to adjust/test metal detectors during manufacture. I have some that will balance a detector at two distinct ground balance numbers with a good span, one is colored Blue & the other Black.
Being able to present various detectors with two known reference points, allows exploring how their ground balance systems relate to one another without having to worry about the variability of real soil comparisons.
Below is a table comparing the GB points using these Ferrites with the Fisher F70 using the stock concentric coil, and the Minelab X-Terra X70 using the stock concentric coil. The testing was done outdoors at 50% sensitivity with the coils 90 deg to and 3 ft above the ground, and the Ferrite bobbed during the Ground Balance procedure for each detector. It should be obvious that the detectors numerically adjust in different directions for positive & negative. i.e. 10 on the X70 is about 90 on the F70 and vice versa.
[attachment 118744 GroundPhaseMap.gif]
As can be seen with the F70 having an adjustment range of 0 to 99 and the X70 0 to 90 makes mapping them quite easy. Overall just a ~10% variance. In the table the span(Difference Column) between the two Ferrite balance points 33 & 34, is nearly identical. And there has been some discussion in the past about the X70 running out of GB range tending towards 0(zero). The bottom row of the table shows that the F70 would also likely run out of range as there is only one number difference.
Below I have included a portion of the F70 manual which discusses ground types. It shows that the two Ferrites Blue & Black provide valid GB points that are likely to be found in real soils. As the exact same wording is found in the Fisher F75 manual, there is a strong possibility that the an F75 fitted with the 10 inch concentric coil would map in a very close fashion.
DIRT
The DIRT bar graph on the LCD display indicates the amount of magnetic mineralization. The
searchcoil must be in motion to measure mineralization. The most accurate measurement is
obtained by pumping the searchcoil, as in the Ground Balancing procedure.
The two-digit GROUND PHASE number displayed on the LCD indicates the type of ground
mineralization.
Some typical ground mineralization types are:
0
Being able to present various detectors with two known reference points, allows exploring how their ground balance systems relate to one another without having to worry about the variability of real soil comparisons.
Below is a table comparing the GB points using these Ferrites with the Fisher F70 using the stock concentric coil, and the Minelab X-Terra X70 using the stock concentric coil. The testing was done outdoors at 50% sensitivity with the coils 90 deg to and 3 ft above the ground, and the Ferrite bobbed during the Ground Balance procedure for each detector. It should be obvious that the detectors numerically adjust in different directions for positive & negative. i.e. 10 on the X70 is about 90 on the F70 and vice versa.
[attachment 118744 GroundPhaseMap.gif]
As can be seen with the F70 having an adjustment range of 0 to 99 and the X70 0 to 90 makes mapping them quite easy. Overall just a ~10% variance. In the table the span(Difference Column) between the two Ferrite balance points 33 & 34, is nearly identical. And there has been some discussion in the past about the X70 running out of GB range tending towards 0(zero). The bottom row of the table shows that the F70 would also likely run out of range as there is only one number difference.
Below I have included a portion of the F70 manual which discusses ground types. It shows that the two Ferrites Blue & Black provide valid GB points that are likely to be found in real soils. As the exact same wording is found in the Fisher F75 manual, there is a strong possibility that the an F75 fitted with the 10 inch concentric coil would map in a very close fashion.
DIRT
The DIRT bar graph on the LCD display indicates the amount of magnetic mineralization. The
searchcoil must be in motion to measure mineralization. The most accurate measurement is
obtained by pumping the searchcoil, as in the Ground Balancing procedure.
The two-digit GROUND PHASE number displayed on the LCD indicates the type of ground
mineralization.
Some typical ground mineralization types are:
0
