How does Ground Balancing Relate to Sensitivity

[landman]

And visa versa. It appears they work together. Do you know how or in what way?

 

[homefires]

Ground Minerals can blind a detector. Bal them out and the detector can see much better.

 

[Reg]

A book could be written to try to answer your question and that is impractical so I will give a very short version as it relates to a PI.

Ground balancing is a form of discrimination where the ground is the item being discriminated out. Get a perfect ground balance (GB) and you get little to no signal from the ground.

When you ground balance you take two samples and subtract one from the other. If the gain of the GB sample is set such that the signal in the GB channel matches the main signal, the ground is cancelled. Unfortunately, any and all objects that have a very similar signal to that of the ground can and will be reduced in sensitivity also.

So, any other object can easily have its signal strength reduced by this GB subtraction process.

On a TDI or one of its basic similar designs, signals will be either high tones or low tones. Which tone they are depends upon how that target's signal compares to the ground signal or the GB channel setting if the GB is not at proper GB.

If we assume the detector to be properly GB'd, then any object with a shorter time constant will have a high tone and those with a longer time constant will have a low tone. The greater the difference in the time constant of a different object than the ground, the less the sensitivity loss.

On a VLF the design is closer to the discrimination feature where you set the disc to ignore certain targets. Those having less conductivity will be ignored and those having a higher conductivity will sound off.

Now, this disc feature will have an effect when using the motion mode of a typical VLF and can cause depth loss if the target is quite close to the characteristics of that at which the disc is set to ignore.

This is an overly simplified explanation where two signals are used to create the GB and at GB, the ground is ignored and any signal that closely resembles the ground can be also ignored or at least reduced in sensitivity. The greater the separation between the ground and the target signal the less sensitivity is lost.

Reg