The step by step build of the Delta Pulse Rev. 5

[Carl-NC]

This is not just an RL circuit, it's an RLC circuit. In fact, it's an R(r)LC circuit, like this:



The resistance of the coil (r) contributes to the Q of the coil itself like this:



so in this case, a smaller r yields a higher Q. But this isn't the R that is driving the coil. If you assume r=0 (ideal wire) then what we are left with is a Thevenin equivalent parallel RLC circuit:



The Q for this is exactly the inverse:



so a large R increases the Q. You can easily see this by trying 1k, 10k, 100k, and 1M resistors. All give about the same answer but higher values make the peak more abrupt and easier to zero in on. I find 1M to make things overly sensitive to connection quality so I tend to stick with 100k.

Sorry, I had not watched Woody's video, it appears to be wrong. His result of 2.58MHz certainly suggests wrong.

[boilcoil]

Woody's method and results, shown in the video, are completely wrong.
The nature of the measured voltage (actually this is the current through the coil) is for series resonance, while the real parasitic capacitance of the detector coil is a distributed parallel capacitance.
Most likely, the obtained data shown in the clip is influenced by the capacitance of the connected probe and the input capacitance of the oscilloscope, which in this case are connected in series to the coil (and in parallel to the added resistance). All of this could in practice be considered a kind of band-pass filter with a natural frequency equal to the measured one.

[Carl-NC]

Most likely, the obtained data shown in the clip is influenced by the capacitance of the connected probe...

What I was thinking as well. His 2.58MHz for a typical 300uH coil suggests 12.7pF, which is in the ballpark of an oscope probe.

[Infamy]

Calculation for damping resistor.

Rd = Damping Resistor value in ohms
f = SRF in Hertzs
L = Inductance Henrys
Pi = 22/7

Rd = Pi x f x L
Rd = (22/7) x 420000 x 0.000731
Rd = 965 ohm

Now thicker wire gives less resistance and a higher Q factor.
This can be applied to water flow.
It can even be applied to US politics.

EE44
Electroniques Educational 44
Research on the top, free education in the middle, shop on the bottom, located next to the elephant, supported by online component sales.
https://www.globetrotter.de/filialen/koeln/ blueprint.

[GeoMax]

Hello Infamy

Calculating Rd is one thing. However, I would use a test circuit to determine the optimal value for Rd with an oscilloscope. Watch this YouTube video for a brief explanation of how to use the test circuit to find the correct damping resistor value for your circuit.

Pulse Induction Damping Resistor Jig - YouTube

[Laith]

Any one can give me the files ?

[Carl-NC]

Do a search for Delta Pulse, everything is posted.