Folks have been askin' for some information on selecting Ground Filters. Most are askin' about Sweep Speed.
The below chart will help you select the best Ground Filter for your sweep speed. If you want to take into consideration Ground Mineralization and EMI, then the chart will help point you in the right direction using those factors as well.
How to read the chart ..... Let just take a couple of examples.
Using ONLY Sweep Speed:
.5 to 1.25 fps = 5Hz
1.5 to 1.75 fps = 7.5Hz
2.0 to 2.25 fps = 10Hz
2.5 fps and up = 12.5Hz
A "rule of thumb" to remember is:
Ground Filter = Sweep Speed X 5.
Using ONLY Mineralization:
Very Low Mineralization = 5Hz
Low Mineralization = 7.5Hz
Moderate Mineralization = 10Hz
High Mineralization = 12.5Hz
Using ONLY EMI:
Low = High Pass
Higher EMI = Bandpass
If your sweep speed is 1.65 fps then you would want to use the 7.5Hz filter. (1.65 X 5) = 8.25, which is closer to 7.5 then it is to 10.
Like my previous Recovery Delay chart, this information is meant ONLY to "get you close". YOU decide what factors you want to drive the filter selection. Then, optimize your settings in the field.
I will offer one suggestion .... You CAN change your physical sweep speed ....
You CAN'T do anything about Ground Mineralization or EMI. If you find yourself in a HIGH Mineralization and HIGH EMI environment, then you want the 12.5Hz High Pass filter.
In other words, in priority order, select the best filter considering;
o Mineralization first
o EMI next
o Sweep Speed last
Adjust your physical sweep speed a bit for the best target response after selecting the best filter for the environmental conditions.
Hint: At any level of mineralization, the slowest sweep speed that you are comfortable with will generally produce the best results. A "good average" sweep speed is 1.50 to 2.25 fps.
Hope this is helpful. Da FoX