Bandwidth of tank circuit / General Science and Electronics / Forums

Forums

4hv.org :: Forums :: General Science and Electronics

« Previous topic | Next topic »

Bandwidth of tank circuit

Move Thread

LAN_403

Plasma

Mon Nov 25 2019, 03:48AM

Registered Member #61406 Joined: Thu Jan 05 2017, 11:31PM
Location:
Posts: 268

Hi, I'm trying to workout the inductor and capacitor spec.
At 37khz the current is the lowest with a value of 17mA, at resonance (49)kHz its 30mA and increases after that.
If the current isnt at the lowest at resonance, is the resistance of the inductor or ESR of the capacitor that has changed it.
The inductor is 47uH and capacitor 220nF, how could I workout the Q?
For circulation current back and fourth between capacitor and inductor, what voltage would I need to get 5A?

I would like to know how you got the answer, not just the answer.

Cheers

Sulaiman

Mon Nov 25 2019, 05:12AM

Registered Member #162 Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140

Hi, I'm trying to workout the inductor and capacitor spec.

At 37khz the current is the lowest with a value of 17mA,
at resonance (49)kHz its 30mA and increases after that.

THIS MAKES NO SENSE TO ME
RESONANCE IS WHERE IMPEDANCE IS LOWEST, IF THE INDUCTOR AND CAPACITOR ARE IN SERIES
OR HIGHEST IF THE CAPACITOR AND INDUCTOR ARE IN PARALLEL.

DRAW A DIAGRAM OF YOUR SETUP AS THE DATA IS, TO SAY THE LEAST, ODD.

Plasma

Mon Nov 25 2019, 05:53AM

Registered Member #61406 Joined: Thu Jan 05 2017, 11:31PM
Location:
Posts: 268

Its a parrellel resonance circuit, 37khz is resonance, but 47uH and 220nH is resonance at 49.5khz. The spec of the capacitor is unknown, no datasheet were I got it from, the inductor is 25mOhm resistance.

klugesmith

Mon Nov 25 2019, 06:56AM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1714

Plasma, we can not read your mind. You must learn to slow down and communicate better if you expect ever to work in a team, or contribute to a team.

You may think your words (like "parallel resonant circuit") are an unambiguous description of what you are dealing with.
Maybe so, but they are far from complete.
When you report a current, is that AC or DC? Where in the circuit?
When you report an impedance, it's between which nodes? WHere and how did you measure the voltage and current?

Plasma

Mon Nov 25 2019, 11:17AM

Registered Member #61406 Joined: Thu Jan 05 2017, 11:31PM
Location:
Posts: 268

Sorry you two. I'm powering it from a H bridge .the capacitor and inductor are directly soldered at both ends. One wire(blue) from the beam of the H is connected to the top and the DMM is connected to the bottom and the other blue wire, to measure current. For voltage I use a capacitor to block any DC voltage an then it goes to a bridge rectifier. That is used to measure across the top and bottom, with the blue wire connected to the top and bottom. I'm measuring Ac amps, but with voltage DC because of the recover.
For the circuit its just a inductor and capacitor in parrellel connected to a Ac voltage source adjustable from 20-80khz.

I know resistance changes parrellel resonance circuit frequency, and resistance make a more flat top in stead of a pointy top, and voltage from that sets the circulation current.

I don't know how the values are found from the measurement taken.the whole circuit that is ossilator and bridge draw about 400mA just to run from a 12V 1.5A source. Measuring on Ac current from the two blues wires with no external circuit shows between 200-300mA with a open circuit voltage from the recover of 5V.

I removed the bottom connection to the parrellel resonance circuit, and connected a blue wire to the bottom connection on the inductor and connected that and the bottom of the capacitor, I measured the Ac current, it was mostly zero until a value jumped out 12mA, that was 49.6khz.
I swapped over the bottom connection from inductor to capacitor with the DMM joining them, as I increased the frequency up to 80khz it read 290mA, I'm guessing because the capacitor would pass more current at higher frequency, but the inductor one, more like resonance effects.

Its abit at odds with each other.

2Spoons

Mon Nov 25 2019, 09:39PM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615

Mate, how old are you and whats your level of education? It would help put some context to your posts. I'm asking because your repeated, badly explained questions are clearly starting to annoy people. I mean - I've NEVER seen Sulaiman post in caps before!

p.s. a little research would go a long way - the answers you seek are out there, and you need to learn to find them, rather than just asking everything here.

I don't mind answering questions, so long as I don't have to spend an hour working out precisely what is being asked., and so long as the asker has clearly put in some legwork of their own.

Plasma

Mon Nov 25 2019, 10:05PM

Registered Member #61406 Joined: Thu Jan 05 2017, 11:31PM
Location:
Posts: 268

All good 2Spoons. Got kicked out of school at 16, next year went to polytechnic for 3 years when I turned up studying for a diploma in computers. 4 years later did a one year engineering course with wielding and fabrication, passed. Had so many jobs in complete different areas. I always was never good at English or spelling. I'm about 33

Moderator(s): Chris Russell, Noelle, Alex, Tesladownunder, Dave Marshall, Dave Billington, Bjørn, Steve Conner, Wolfram, Kizmo, Mads Barnkob