PI Power Output

[Qiaozhi]

One theory says that the TX pulse needs to be long enough to fully energize the target. without getting into too much details, a target with a TC of 100 uS, would need about 3 TC or 300uS TX pulse to be practically fully energized.

Others say that the switch OFF transient is what energizes the target. The switch OFF transient is very short but powerful, but what about the time to energize the target? Is the energizing TC of the same duration as the decay TC?

Tinkerer

This is a popular misconception. During the time when the current is being established in the TX coil, the target is not being charged. The generation of eddy currents in the target occurs when the "switch" opens. Of course there is some eddy current generation during switch-on, but it is small when compared to switch-off, and plays no part in target detection. The switch-on period needs to be of long enough duration to establish a sufficiently strong magnetic field around the coil. It is the collapsing field that does the work, not the other way round.

[Tinkerer]

Fully energize target

You are correct, the higher the PPS the more noise is averaged out of the integrators. But the trade off at high PPS is that the Tx might not long enough to fully energize long Tc targets?

I would like to revisit and revive the "fully energized target" discussion.

There are several theories, I used to be convinced of one theory, but recent experiments I made seem to indicate that it is not so.

One theory says that the TX pulse needs to be long enough to fully energize the target. without getting into too much details, a target with a TC of 100 uS, would need about 3 TC or 300uS TX pulse to be practically fully energized.

Others say that the switch OFF transient is what energizes the target. The switch OFF transient is very short but powerful, but what about the time to energize the target? Is the energizing TC of the same duration as the decay TC?

Tinkerer

Intuitively, using a higher PPS, but with the same power consumption, should produce a better S/N.
Example: 100 PPS with long TX, using 1W total consumption.
Or: 1000 PPS with short TX, using 1W total consumption.
With 1000 PPS you can average 10 times more signal samples. This should better the S/N considerably.
But what is the reality?
What does the Math tell?
Anybody willing to do an analysis?

Of course, after that it will also depend on the way the signal is processed.

Tinkerer

You are correct, the higher the PPS the more noise is averaged out of the integrators.But the trade off at high PPS is that the Tx might not long enough to fully energize long Tc targets?

[Tinkerer]

TX power

To increase the depth by 100% you need I believe about a 64 fold increase in power delivered to the coil or as Carl more correctly says ampere/ turns.Imagine the size of the battery! What matters is the S/N! Increasing the voltage /current raises things like Johnston noise, may stress IC's etc and lead to an ever poorer S/N! Also any detector must conform to a countries EMI emission standards, this gets much , much harder as the power goes up.So in summary more is often LESS!!!

Intuitively, using a higher PPS, but with the same power consumption, should produce a better S/N.
Example: 100 PPS with long TX, using 1W total consumption.
Or: 1000 PPS with short TX, using 1W total consumption.
With 1000 PPS you can average 10 times more signal samples. This should better the S/N considerably.
But what is the reality?
What does the Math tell?
Anybody willing to do an analysis?

Of course, after that it will also depend on the way the signal is processed.

Tinkerer

Hi All,

What is an "average" control box power output figure to the TX coil?

Eg:
Voltage & Amps

Is there a limit on what this power output should be or is it a case of the more the better type senario?

Is there a preferred Power output figure for some reason?

To increase the depth by 100% you need I believe about a 64 fold increase in power delivered to the coil or as Carl more correctly says ampere/ turns.Imagine the size of the battery! What matters is the S/N! Increasing the voltage /current raises things like Johnston noise, may stress IC's etc and lead to an ever poorer S/N! Also any detector must conform to a countries EMI emission standards, this gets much , much harder as the power goes up.So in summary more is often LESS!!!

[B^C]

Hi All,

What is an "average" control box power output figure to the TX coil?

Eg:
Voltage & Amps

Is there a limit on what this power output should be or is it a case of the more the better type senario?

Is there a preferred Power output figure for some reason?