Made another go at this since I worked a few chapters in my text book

Wiring this old artifact ballast in series with a 1000 ohm resistor and putting variable frequency through it.  With predictable results 

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So now when people see me wandering around wondering what I'm thinking about it's gonna be....."so the resistance of the inductor (ballast) goes up.....

I remembered I had a monster choke so I went and grabbed it and repeated the tests


The results were not what I expected it is such a beast I figured it would have crazy reactance a lower frequency

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But it let me go much higher

 

I have a lot to 💬 ponder 

Btw I used an atlas lcr45 on the ballast it measured about 755 mH

So on the label on the monster choke I guess hys means Henrys then it's 5 mH 

I have very small 10 and 15 mH inductors so why is a 5 mH so big and heavy 🪨 

Edit: because it can handle 22.5 amps and 1500 volts

So then I'm doing a bunch of problems where the output voltage ⚡ is divided by the input voltage at different frequencies and do some more calculations with logarithms etc and it gives me the frequency response (?).....in decibels...?

I thought decibels was like dude how loud 🔊📢 is stuff.  Like a 70s Who concert or 707 taking off.

Oh well back to the grind 

I'm doing lots of the same stuff over and over with resistors capacitaters and inductors 

I've been impressed with this hobby that experimental results closely match calculations.

However I'm wondering if there is a limit to how accurately my multimeter can measure ac voltage ⚡ drops (rms) at different frequencies....like 20 khz

Oh well I guess that's why we have oscilloscopes (Vp-p)

Or bench multimeters ? 

I'm sure it would be cool 😎 to have a bench meter but I certainly don't need voltage to twenty decimal places or a real earth ground (thanks G1  )

Your meter should have a spec for the AC volts range as far as frequency response.
My true RMS meter says 45Hz to 2Khz.  A lot of them are just for measuring AC volts in the 60 to 100Hz area.
Yes, scope is best bet for higher freqs.

Here is an 🥼🧪 experiment I just did

I was really impressed how the measured hung right in there with the calculated

Unfortunately at 50 khz it went out the window
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Here is the "schematic" 

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I know

I should have remeasured everything with my scope.   

Ok I went and redid the experiment this time using my scope to measure the voltage drop across the resistor at different frequencies and got some good results 
(bottom left)
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gratuitous scope pic

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So all I need now is a gif of Keanu going
"DUDE.....your meter can't handle it "

 

Well I got into somewhat of a pickle 🥒

I have three chapters to go in my little book before I can go on to the cool second book that has me playing with transistors and diodes and stuff but I hit a 🛣� roadblock.

The third from the last chapter was on bandpass filters so I ran into trouble with the impedance calculations of inductors and capacitaters and resistors in parallel.  Meanwhile I was like "what is all this j and theta crap" 

I tried to get through it but ultimately admitted defeat and went back to a chapter in a book a did a few years ago so I'm midway through that.
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So all good it should be rewarding to get to the lab portion and see 🙈 how the 🥼 experimental 🧪 results compare.

There is a post by one of our esteemed members from near Australia 🦘 🌏 where he told someone what frequency to expect from a potentiometer and capacitater  so I may play around and see if I can figure out how he calculated that   

Ok I tried it 
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I got lucky I guess 

Might be time to buy a lottery ticket 

I just cheat and find a calculator on the net.
http://www.learningaboutelectronics.com/Articles/High-pass-filter-calculator.php
http://www.learningaboutelectronics.com/Articles/Low-pass-filter-calculator.php
http://sim.okawa-denshi.jp/en/Fkeisan.htm

I'm glad you were nice
I actually got scared when I saw you replied 

 

Quote from: Tassieviking on January 30, 2025, 10:47:14 AMI just cheat and find a calculator on the net.
...
http://sim.okawa-denshi.jp/en/Fkeisan.htm

This is the one that I use!

About forty years ago when I was still in college and working part time the university had afternoon/evening classes I guess it was geared towards working older people 

So anyway I was a 🦇 vampire staying up all night doing homework and playing guitar 🎸 etc and my routine had me going to bed 🛏� at about 0530.  I had found that Casper the friendly ghost 👻 came on like at 0500 and that was my SOP.

So what does all that have to do with anything? 
At night in the small town it got quiet with the exception of an audible hum 
Sometimes I would have the windows open I was in an upstairs room at the end of the house.  This (real or perceived) hum/pitch/monotone frequency tormented me to some end.  In fact I made a few nocturnal excursions around town looking for it.  I would drive around to different areas and shut the engine (slant six 66 Dart) off and sit and try to determine where it was coming from.
Spoiler alert: I never did find it or find out anything.
When I told my dad about it he said there was a composer that went crazy because of constantly hearing 440 or something 

Quote from: saturated on February 02, 2025, 05:43:03 AMAbout forty years ago when I was still in college and working part time the university had afternoon/evening classes I guess it was geared towards working older people 

So anyway I was a 🦇 vampire staying up all night doing homework and playing guitar 🎸 etc and my routine had me going to bed 🛏� at about 0530.  I had found that Casper the friendly ghost 👻 came on like at 0500 and that was my SOP.

So what does all that have to do with anything? 
At night in the small town it got quiet with the exception of an audible hum 
Sometimes I would have the windows open I was in an upstairs room at the end of the house.  This (real or perceived) hum/pitch/monotone frequency tormented me to some end.  In fact I made a few nocturnal excursions around town looking for it.  I would drive around to different areas and shut the engine (slant six 66 Dart) off and sit and try to determine where it was coming from.
Spoiler alert: I never did find it or find out anything.
When I told my dad about it he said there was a composer that went crazy because of constantly hearing 440 or something 

Was there a hydro-electric power plant nearby at all?  Or did the college have a steam plant?  They create hum like you are describing.  UMaine Orono has a steam plant, and a lot of northern colleges do.  Not sure about out your way.