Author Topic: Tektronix 2225  (Read 25396 times)

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Offline Mechatrommer

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Re: Tektronix 2225
« Reply #25 on: October 18, 2010, 03:52:26 pm »
if i just create a on and off program with out a delay.. that will get me 10 Mhz right? wil that be fast enough?
the fastest i can crack the Arduino to generate frequency using assembly is MIPS/4 (4 ops). so if AT1280 is at 16MHz, it only capable of generating 4MHz signal. but thats in assembly. In Arduino IDE? digitalOut? dont dream it! i can say the overhead will be like 36 ops (the fastest).
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline JohnS_AZ

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Re: Tektronix 2225
« Reply #26 on: October 18, 2010, 03:56:05 pm »
You could whip together a quick 555 oscillator circuit that would give you a number of signals to view on your scope.

http://www.kpsec.freeuk.com/555timer.htm
I'm either at my bench, here, or on PokerStars.
 

Offline Mechatrommer

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Re: Tektronix 2225
« Reply #27 on: October 18, 2010, 04:15:20 pm »
You could whip together a quick 555 oscillator circuit that would give you a number of signals to view on your scope.
http://www.kpsec.freeuk.com/555timer.htm
yup! to get faster signal, you should go analog, or... "Op Amp Hours"!
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline saturation

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Re: Tektronix 2225
« Reply #28 on: October 18, 2010, 04:56:39 pm »
If that video is true, that scope looks to be in great shape.  A super steal for $75.
Best Wishes,

 Saturation
 

Offline SuperMiguel

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Re: Tektronix 2225
« Reply #29 on: October 18, 2010, 05:00:38 pm »
You could whip together a quick 555 oscillator circuit that would give you a number of signals to view on your scope.

http://www.kpsec.freeuk.com/555timer.htm

Hoe fast should I make it?
 

Offline Mechatrommer

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Re: Tektronix 2225
« Reply #30 on: October 18, 2010, 05:21:57 pm »
Hoe fast should I make it?
quick check the datasheet indicates 555 only run up to 500KHz. but i can be mistaken. so i'll leave the detail to the original suggestor. here is one basic op amp thread thats good for beginner like me https://www.eevblog.com/forum/index.php?topic=791.0. maybe you can check the Arduino Oscillator pins to get faster signal, but should make the V/div to minimum i think.
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline JohnS_AZ

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Re: Tektronix 2225
« Reply #31 on: October 18, 2010, 05:32:39 pm »
A 0.1uF cap and (R1+2R2)= 1Kohm should put you about 10KHz, which should do find to see stuff on your scope.

Here's another site that I refer to frequently when I'm mucking around with 555 circuits....

http://home.cogeco.ca/~rpaisley4/LM555.html
I'm either at my bench, here, or on PokerStars.
 

Offline SuperMiguel

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Re: Tektronix 2225
« Reply #32 on: October 19, 2010, 04:00:23 pm »
A 0.1uF cap and (R1+2R2)= 1Kohm should put you about 10KHz, which should do find to see stuff on your scope.

Here's another site that I refer to frequently when I'm mucking around with 555 circuits....

http://home.cogeco.ca/~rpaisley4/LM555.html

will use one of this http://www.radioshack.com/product/index.jsp?productId=2102589 have to go purchase it today, and test
« Last Edit: October 19, 2010, 04:10:08 pm by SuperMiguel »
 

Offline SuperMiguel

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Re: Tektronix 2225
« Reply #33 on: October 19, 2010, 11:57:05 pm »
So i made a 555 timer using 2 x 330 ohms resistors and a 0.1uf cap using a 9v input which gives me a 14KHz frequency...

So i set my oscilloscope to: Sec/Dvi = 20 microseconds and 10V on the 10x probe and got:



why is it flickering?
 

Offline allanw

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Re: Tektronix 2225
« Reply #34 on: October 20, 2010, 12:06:28 am »
Could be unstable triggering? Try playing with the trigger level.
 

Offline joelby

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Re: Tektronix 2225
« Reply #35 on: October 20, 2010, 12:09:24 am »
I'd also try looking at it over a long time scale (50, 100, 1000ms/div, etc.) to see if the oscillation remains stable over time, or if it's stopping and starting.
 

Offline SuperMiguel

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Re: Tektronix 2225
« Reply #36 on: October 20, 2010, 12:22:12 am »
Could be unstable triggering? Try playing with the trigger level.

That was it :)

 

Offline JohnS_AZ

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Re: Tektronix 2225
« Reply #37 on: October 20, 2010, 12:35:11 am »
Awesome  :)  And congrats, seems like that scope was a great score!
I'm either at my bench, here, or on PokerStars.
 

Offline Mechatrommer

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Re: Tektronix 2225
« Reply #38 on: October 20, 2010, 04:11:44 am »
the flickering thing seems unusual. its like some power surge in our home and our lamplights start flickering ???
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline SuperMiguel

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Re: Tektronix 2225
« Reply #39 on: October 20, 2010, 01:11:07 pm »
the flickering thing seems unusual. its like some power surge in our home and our lamplights start flickering ???
Whats the deal with ground?some people tell me that yhe scope is grounded directly to the wall jack and that I should not need the ground cable, but if I dont use it, I cant get a signal...
 

Offline DJPhil

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Re: Tektronix 2225
« Reply #40 on: October 20, 2010, 02:00:48 pm »
Whats the deal with ground?some people tell me that yhe scope is grounded directly to the wall jack and that I should not need the ground cable, but if I dont use it, I cant get a signal...
Ground is just a reference potential. The safety ground of the scope is the scope's reference, true, but most low voltage circuitry will be at a different (usually oscillating due to noise) potential. By linking the two grounds they're both working from the same reference.

Think of it this way, say you switch the scope to DC coupling and put the probe on the positive terminal of a 9V battery. Nothing happens, or at most you get some noise. There's nothing completing the circuit from the other side of the battery to the scope (or saftety ground), so the scope can't measure anything. The battery is at a 'floating' voltage, the grounds are unrelated. By connecting the probe ground you complete the circuit. You could connect the negative terminal of the battery to safety earth and get the same result, but there would be a lot more noise because the current has a huge loop (antenna) to flow through.

To see this effect in action, try setting your scope to about 200mV/div (AC or DC coupling) and touch the end of the probe with your finger. This is the same as holding the tip of a cable attached to a guitar amp. That horrid buzzing is now a waveform on your screen. You may have to do some work to dial it in, and you'll see it best if you switch your trigger to 'Line' (triggers directly off of the AC line voltage). This is a floating measurement using you as an antenna. Try the same thing with one hand near a dimmable light or adjustable fan and you'll see the horrid waveforms that triacs emit.

Any circuit that's referenced to safety earth (ground or otherwise) won't require the probe ground, but it's still useful. By using it you cut out a huge amount of loop area and cut your noise down to a minimum. In a floating circuit you can also take differential measurements between any two points because you're free to define your measurement ground by whatever you clip your probe ground to. For example you could swap the battery around and you'd get negative 9V on your scope (well, a bit more than 9V, check a fresh one with a meter to see what I mean).

Hope that helps some. If I messed anything up I'm sure folks will set me right. :)
 

Offline Mechatrommer

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Re: Tektronix 2225
« Reply #41 on: October 20, 2010, 02:41:49 pm »
the flickering thing seems unusual. its like some power surge in our home and our lamplights start flickering ???
Whats the deal with ground?some people tell me that yhe scope is grounded directly to the wall jack and that I should not need the ground cable, but if I dont use it, I cant get a signal...
no it got nothing to do with ground. what i meant is, its analogous to the Home Main Power Surge. maybe something is playing up inside, dead caps maybe? i dont know, that cause the flickering. ???
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline SuperMiguel

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Re: Tektronix 2225
« Reply #42 on: October 20, 2010, 03:18:03 pm »

the flickering thing seems unusual. its like some power surge in our home and our lamplights start flickering ???
Whats the deal with ground?some people tell me that yhe scope is grounded directly to the wall jack and that I should not need the ground cable, but if I dont use it, I cant get a signal...
no it got nothing to do with ground. what i meant is, its analogous to the Home Main Power Surge. maybe something is playing up inside, dead caps maybe? i dont know, that cause the flickering. ???


Well yhe flickering was fixed by adjusting the trigger level
 

Offline Mechatrommer

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Re: Tektronix 2225
« Reply #43 on: October 20, 2010, 03:26:22 pm »
Well yhe flickering was fixed by adjusting the trigger level
oic. from the video you provided, it seems to me that the trigger level is set correctly, just flickering. now i think i'm start to envy you, its lucky for you there is local guy to sell such thing. as other said, its super steal! now suggestion: to improve the value of it, maybe you can fix the dented screen frame on the top left, so your scope will looks much better and... like new! ;D ;)
« Last Edit: October 20, 2010, 03:35:45 pm by shafri »
if something can select, how cant it be intelligent? if something is intelligent, how cant it exist?
 

Offline SuperMiguel

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Re: Tektronix 2225
« Reply #44 on: October 20, 2010, 06:01:50 pm »
So i installed Audio ToolBox to generate few signals from my audio card and i have a question so i set the sine wave to 10KHZ:


and i get:

or

if i change the type from sine to square i get:


why is that?? why im not getting a square wave??
 

Offline allanw

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Re: Tektronix 2225
« Reply #45 on: October 20, 2010, 06:05:15 pm »
If your sound card is set at a sampling rate of 44100Hz (which is usually the default), it'll only be able to produce frequencies up to 22kHz. A square wave is made up of a sum of sine waves (see: Fourier series), with the main contribution being the original frequency, and other harmonics at odd multiples of it. Since 30kHz signals can't show up from your sound card, it'll look weird like that.
 

Offline SuperMiguel

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Re: Tektronix 2225
« Reply #46 on: October 20, 2010, 06:14:48 pm »
If your sound card is set at a sampling rate of 44100Hz (which is usually the default), it'll only be able to produce frequencies up to 22kHz. A square wave is made up of a sum of sine waves (see: Fourier series), with the main contribution being the original frequency, and other harmonics at odd multiples of it. Since 30kHz signals can't show up from your sound card, it'll look weird like that.

set it to 5KHz and
« Last Edit: October 20, 2010, 06:26:01 pm by SuperMiguel »
 

Offline allanw

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Re: Tektronix 2225
« Reply #47 on: October 20, 2010, 06:22:33 pm »
Please see this: http://en.wikipedia.org/wiki/Fourier_series

A 10kHz square wave can be decomposed into a sum of sine waves of frequencies 10kHz, 30kHz, 50kHz, etc. The higher frequencies are what makes it look like a square wave instead of a sine.

edit: your 5kHz square wave looks as expected. Looks like the second image here, which is the sum of sine waves of the original frequency and at 3 times the original frequency: http://en.wikipedia.org/wiki/File:Fourier_Series.svg

The higher frequencies, at 5 * 5kHz, 7 * 5kHz won't show up.
« Last Edit: October 20, 2010, 06:34:53 pm by allanw »
 

Offline saturation

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Re: Tektronix 2225
« Reply #48 on: October 20, 2010, 06:40:30 pm »
You're getting closer.  To get a square looking wave, divide the top most frequency by ~ 10, its really the 9th harmonic, but 10 is easier to remember.  If you can generate and see without distortion, the highest harmonic, then you can likely see all the top intervening harmonics too: 3,5,7,9.

If the top frequency is 22kHz, to see a nice sq. wave use ~ 2kHz.

If your sound card is set at a sampling rate of 44100Hz (which is usually the default), it'll only be able to produce frequencies up to 22kHz. A square wave is made up of a sum of sine waves (see: Fourier series), with the main contribution being the original frequency, and other harmonics at odd multiples of it. Since 30kHz signals can't show up from your sound card, it'll look weird like that.

set it to 5KHz and
« Last Edit: October 20, 2010, 06:42:12 pm by saturation »
Best Wishes,

 Saturation
 

Offline Strube09

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Re: Tektronix 2225
« Reply #49 on: October 20, 2010, 06:42:11 pm »
Yep... looks about as good as a sound card could probably produce... I bet at around 1K it would look almost there. ... just depends on how many harmonics the sound card can produce at once.... if it will only produce 4 or 5 odd harmonics at once then you probably won't get much better.
 


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