My first scope

[lykkedk]

Hi all.. I got lucky today, caught my first scope.
Planning to use it for meassuring PSU - maybe GAIN / Dissorton whatever...
It's a Kenwood cs-1021 - Anybody got something for it (manuel etc...)

I got some quistion's through.

I need to buy a 'probe' for it : The input BNC say's 1MOhm / 35pF.
// ( I don't care if the probe is used or not, so if you have an used one for sale, I might be interrested.) //

Is there anything I have to consider, buying my probe.

--> Any comment's allowed. - All information appreciated. <--

BTW:I know it's a 'cheap' scope, but I think it's better than nothing at all !

 

[Rob Thomas]

I need to buy a 'probe' for it : The input BNC say's 1MOhm / 35pF.

$19.99 Buy It Now 60 MHz probe (1 MOhm) on eBay linked below. Check out his store, great deals on soldering/electronics tools, tweezers, pliers, snips, etc. He has faster probes, but you don't need 'em.

http://tinyurl.com/ee4g8

 

[anatech]

Hi lykkedk,
That's a nice 'scope you have there. It will do most of what you need to do in audio. It even looks like it has a 0.5uS / Div horizonal setting. That means you could use it for setting up CD players easily.

Kenwood is a good brand too, so don't sell it short.

-Chris

 

[lykkedk]

The probe in ebay, dosen't offer shipping to Denmark.

Anyway... It's a good price through.

 

[anatech]

Hi Jesper,
How much are the original Kenwood probes from the local supplier? The scope is worth using good probes with.

-Chris

 

[lykkedk]

I don't know, but i just ordered one today (~30Euro incl. shipping cost)

The shop, told me, it was fine for my scope.

 

[anatech]

Hi Jesper,
Just make sure the probe covers the bandwidth of your 'scope minimum.

X1 probes are not suitable, you want a X10 most commonly (you can get X100). The better probes will last longer.

-Chris

 

[lykkedk]

Its a 1x / 10x Allround probe.

You can see it here.

Anyway, I was googling around for a sinwave generator - or simulair. What excatly do i need to messure e.g gain ? Any link for DIY sinusgen. ?

 

[anatech]

Hi Jesper,
That probe should do you well. Watch you leave it on X10.

Look for something like a Leader LAG120 A or B. Reasonable output distortion. Some of the solid state old HP generators are good too but they may even be more expensive than the Leader. Kenwood may make essentially the same model. Function generators have poor sine wave output, sometimes the square wave isn't very good either. Snag one only if you find it used and cheap, look for a good sine wave generator. The Leader does square waves too.

-Chris

 

[I_Forgot]

You can use a CD player with a test CD to generate clean, low distortion sine waves.

I_F

 

[lgreen]

***
Anyway, I was googling around for a sinwave generator - or simulair. What excatly do i need to messure e.g gain ? Any link for DIY sinusgen. ?

You don't need one. dowload some audio test signals from my personal website and burn them to CD or play back from your PC. I've got a few sinewaves in there.

These were burned right from a Tektronix FG501. If you want to create your own waves, search for 'function generator' on google.

Nice scope, it will be a very useful tool.

To measure gain, measure the amplitude of the input and of the output. And see how much they differ.

I think gain in dB = 20log (Vout/Vin).

Do this at different frequencies and you can check the roll-off of the device being measured.

 

[anatech]

You can use a CD player with a test CD to generate clean, low distortion sine waves

True, but if it skips while doing a THD test you'll pin the meter. The tone also runs out at the wrong time and changing frequency is a pain.

You might be further ahead to use your sound card, but I'll recommend an audio generator still.

-Chris

 

[lgreen]

True, but if it skips while doing a THD test you'll pin the meter. The tone also runs out at the wrong time and changing frequency is a pain.

-Chris

Pin what meter? He has a scope not a THD meter. Nothing to pin there.

I agree, test tones on CDs are short and run out at the wrong time, that is why I've uploaded 1 minute tones that anyone can download. A lot of data but a nice long tone.

 

[anatech]

Why lgreen,
I'm merely thinking of the future when he gets one.

I should have congratulated you on linking to the files. That was nice of you to offer them. I have tried that route and guess what? I have a THD meter, and when on low scales any change may pin the needle pretty good. I hate that sound. I don't use the test CD anymore for that.

-Chris

 

[lgreen]

Why lgreen,
I'm merely thinking of the future when he gets one.

-Chris

Ooooohhhh.

I was thinking of the present-- he needs some nice wiggly signals to try his brand new used scope on!

So is the motto of the story that when using a THD meter you should only use a function generator? I can certainly see valid reasons for that!

 

[lykkedk]

Thank you all for some nice answer's. - I will try the 1Khz testtone today, to see how it look's

I will continue searching for an DIY tonegen.

 

[lgreen]

For a very nice DIY tone generator search for a-

"Wein Bridge Oscillator"

Wein Bridge at ESP, #22

This one of the most famous circuits in history. It is the circuit that William Hewlett and Dave Packard first implemented (with a twist and lightbulb) which begat the Hewlett Packard Company.

It is simple and you will find a lot of modern implementations.

 

[shusha]

Or you may be more ambitious and build one with Maxim's MAX038 function generator. There are numerous schematics laying around, even a few usefull in the datasheet.

I have decided to build one from EPE magazine, PIC controlled with freq. meter.

An externally hosted image should be here but it was not working when we last tested it.

 

[lykkedk]

EDIT : Look good to the MAX038, i was writing this, while you have posted

Look's good the ESP 22 project.

As I see it, I will need to build either the Lamp Stabilised Wien Bridge Oscillator, or the Thermistor Stabilised Version.

After that I have to connect, Level Control And Attenuator / Square Wave Generator.

What I do not quite understand is as follows:

1. As I see, it, it just need to be connected to +12 gnd -12 VDC. Right ??

// From the website

The oscillator is designed to operate using the AC "plug-pack" power supply described in Project 05, since this is simple and safe. The output level is adjustable in 20dB steps, from a maximum of +10dBV down to -50dBV in 4 ranges as shown in Table 1, with a variable control to enable any desired voltage from 0V up to the maximum.

// To here.
// I don't quite understand the meaning of this ??? Is it the output attenuator, who doe's this DB control ???

2. project 5 is just a PSU, witch could be used to it, no need to build ???
3. Do I need any amplifier to this ???
4. I think I have to build the Lamp Stabilised version, what type of LAMP do i have to use ? AC or DC ? 12v ?


I know it's a little confusing.

 

[anatech]

Function generators can be useful, but I almost never fire mine up anymore. My sine generator (Leader LAG-120B) also outputs a good square wave. A function generator typically will have 0.5% THD or higher with a sine wave. Not terribly useful.

I have built some wein bridge oscillators with FET level control. Really low THD if you match the caps and resistors. This is better than my Leader.

Lgreen:

So is the motto of the story that when using a THD meter you should only use a function generator?

Ahhh, yeah. That's about it. I was trying for a really low distortion signal to confirm CD response. What I need to do is make a 20 minute tone on CD digitally, not recorded from the sound card. I am not able to generate that file so .......... 20 min of 10KHz and 20 min at 20KHz might be interesting.

-Chris