PI-coil dampind resistor

[Anonymous]

If a factory coil has 30 turns of wire.
and you make a new coil with 26 turns of wire, same size coil.
Is it normal to increase restance to damping resistor or lower restance. Thanks.
Frank.

 

[Anonymous]

The formula for critical damping is: R = 2 X the square root of L over C (with L and C under the sq root sign). Draw out that formula; it is much easier to see the relationship that way.
If you reduce L by 3 turns, you reduce C also. You need to measure the resonant frequency of each coil (by sweeping with varing frequencies between 100Khz and 500KhZ) to see the impact of changing the inductance. Just plug the inductance and capacitance into the formula that I provided to see the impact on critical damping. To find capacitance, go to the web sites that helps you calculate inducatance by entering coil diameter and number of turns. Then, calculate the given inductance (from that estimate) with the necessary capacitance to create the resonance frequency that you got from sweeping the coil.
Tight coils, with minimal wire spacing, increase the capacitance and inductance, while coils that are spread apart with thicker insulation have less capacitance but also less inductance. Therefore, measurements are critical to derive your answer.
You probably need a frequency generator (up to 500 Khz) and O'scope to make these calculations.
Based on my the calculation on my own coils, a change of 3 turns may only have a 50 to 60 ohm difference in critical damping.
bbsailor

 

[Anonymous]

http://my.athenet.net/~multiplx/cgi-bin/airind.cgi
Use the .1% answer as it is closer to what is measured.
bbsailor

 

[Anonymous]

Thanks,
I found a easy way to do it that works for me.By putting a temp-ary multie switch at damping resistor with a different R, at each point.By doing this you can adjust damping resistor to coil, detector and ground condition at same time.Hope that you understood my chane of thought.Some people dont get what I say.
Frank.
PS. Are you any good at figureing the number of turns of wire in a coil.The Site mentioned is good for inductions,
I have induction value and size of wire.If I give coil size, inductions and wire size for 10" DD. Can you come up with the amount of turns in coil.
Talk to you after Easter.

 

[Anonymous]

Try the calculator on this site.
http://www3.telus.net/chemelec/Calculators/A-Inductance2.htm
Given what you know about the coil: diameter, wire size and number of turns, this calculator should be helpful.
bbsailor