Coil TX tester for PI pulse?

[bklein]

Has anyone made their own PI TX coil pulse tester?
Just curious, as it would make sense to have such a thing while testing coil performance, drive circuits, and timings.
Would this be a simple air core coil and preamp or ferrite wrapped with wire, what?

Barry

[taliesin]

Has anyone made their own PI TX coil pulse tester?
Just curious, as it would make sense to have such a thing while testing coil performance, drive circuits, and timings.
Would this be a simple air core coil and preamp or ferrite wrapped with wire, what?

Barry

i'm working on such a thing at the moment.
makes sense to me

[mikebg]

Barry, when we use a test turn connected to a scope, the scope shows only the derinative of TX current i, ie
e=k(di/dt),
where k depends on geometry (number of turns, turn diameter and distance).
The voltage across TX coil differs in form from pure derivative because contains in addition a component depending on coil resistance r, ie:
u=i.r,
where i is TX current.
The method with test turn is very convenient for adjustment of damping resistance because changing distance we can observe ringing at full screen.

To observe TX current, we can connect a piece of resistive wire (for example 0.1 ohm) in series with cold lead of TX coil (before cable as shown below). The voltage across this resistor is also convenient for adjustment of damping resistance because there is no flyback voltage.

[taliesin]

question for you mike

does it matter how the test turn is orientated ?

[bklein]

Barry, when we use a test turn connected to a scope, the scope shows only the derinative of TX current i, ie
e=k(di/dt),
where k depends on geometry (number of turns, turn diameter and distance).
The voltage across TX coil differs in form from pure derivative because contains in addition a component depending on coil resistance r, ie:
u=i.r,
where i is TX current.
The method with test turn is very convenient for adjustment of damping resistance because changing distance we can observe ringing at full screen.

To observe TX current, we can connect a piece of resistive wire (for example 0.1 ohm) in series with cold lead of TX coil (before cable as shown below). The voltage across this resistor is also convenient for adjustment of damping resistance because there is no flyback voltage.

I was thinking more in the line of just testing the coil/circuit for distance but your idea has validity for some things. I'm more interested to test the TX signal performance as I were to play with various coil configurations/shields/timings/feedline... You could even stick the sensor in a garbage can of highly mineralized soil (I brought some from Stanton - shows how sick I am) to test with...

Barry

[mikebg]

does it matter how the test turn is orientated ?

Yes, does.
Taliesin, the mutual inductance M between two coils can be positive or negative depending on which lead of test loop is connected to ground of scope.

[taliesin]

i'm going to try this method .thankyou mike

[Mechanic]

Hi Guys,

I use a small coil from an old solinoid, 15mH with a 10nf cap across it. I place this some distance from the coil and use it to test output power from the coil. More power = higher amplitude oscillations in the test coil.

Cheers Mick

[Vortxrex]

You could even stick the sensor in a garbage can of highly mineralized soil (I brought some from Stanton - shows how sick I am) to test with...

Barry

LMAO