waveform checking,testing,frequency response

[Walters]

Does anyone know how to do

1.) Waveform checking procedures?

2.) Testing measurements and what are the terms and names?


3.) Measure impedance for input and output on each stage?
how do i do this with my DMM or Oscilloscope?


4.) Time measurements? phase, pitch,frequency, period


5.) Frequency Response test procedures how do i do them

with a function generator and a DMM or oscilloscope?

[Geoff_T]

Originally Posted by Walters

Does anyone know how to do

1.) Waveform checking procedures?

2.) Testing measurements and what are the terms and names?


3.) Measure impedance for input and output on each stage?
how do i do this with my DMM or Oscilloscope?


4.) Time measurements? phase, pitch,frequency, period


5.) Frequency Response test procedures how do i do them

with a function generator and a DMM or oscilloscope?

Hi

First of all, you can do a lot with a multimeter and a scope but if you want absolute measurements of total harmonic and/or intermodulation distortion and signal to noise ratio, you will need some more sophisticated test gear. A lot of it you can buy on EBay but you have to remember that poorly maintained test equipment is next to useless... like an inaccurate clock.

1. If you have an oscillator capable of producing good square waves, a 1KHz square wave is a very good way of checking an equaliser and response in general. The vertical part of the wave is high frequency and the horizontal part the low frequency response. It also shows if there's ringing if (for instance) a transformer output is feeding a capacitive load.

A scope enables you to measure ac and dc volts and to calculate frequency... the invert of the time base... so 1mS per division and a trace that completes a cycle in a division is a frequency of 1KHz = 1/0.001

2. There are loads... it depends what you want to measure. Nowadays audio analysers do most if not all the tests. When I was at Neve we used a Sound Technology 1710A distortion analyser as as low distortion oscillator and distortion measuring set and a Seinheisser UPM550 Noise meter for noise measurements. Then they went over to Audio Precision test gear operated via PC's and printers that enabled much faster results to be obtained.

3. There's several ways to do this and some modern test gear analyses the impedance. A crude way is to put a pot in series with the input (from a low impedance source that's included in the sums) and increase the value until the signal drops by 6dB (= one half the original level). The impedance of the pot + osc output impedance is the same as the input impedance of the device under test.

4. You've covered this in other questions, specifically the scope part. You can check phase with a scope if you trigger it off the source feeding the device under test. You can also use the input as one trace and the output as t'other and watch the latter move as you apply large amounts of EQ.

5. I gave that info in the bit about using a scope. Your function generator must have a frequency scale on it so you know roughly what the frequency is. I wouldn't trust the ac range on the multimeter to have a flat response so you'll have to use the scope and note by how much the trace reduces at the frequency under test. If it was 5 graduations high and shrinks to 4 (for instance) then it's 4/5's it's original size. 4/5's is 0.8 as a ratio or 20 x log (0.8) = around -1.9dB.

[Walters]

Geoff

i have a oscilloscope , function generator , DMM, power supply


What test proceduces can i do for audio circuits?

Measurements for audio circuits ?
Can you list some measurements i can do
for any audio circuit?

Checking for the noise?

overloading the input measurements?

output power measurement?

Time measurements for clocks and LFO circuits testing the frequency and Time?


Frequency Response curves and measurements Vs voltage drops dbs slopes

for Tone stacks or studio eq rack gear how do i do this?


Current draw of power supplies for studio gear how do i do these tests
and measurements with a Ammeter?

[Geoff_T]

Originally Posted by Walters

Geoff

i have a oscilloscope , function generator , DMM, power supply


What test proceduces can i do for audio circuits?

Measurements for audio circuits ?
Can you list some measurements i can do
for any audio circuit?

Checking for the noise?

overloading the input measurements?

output power measurement?

Time measurements for clocks and LFO circuits testing the frequency and Time?


Frequency Response curves and measurements Vs voltage drops dbs slopes

for Tone stacks or studio eq rack gear how do i do this?


Current draw of power supplies for studio gear how do i do these tests
and measurements with a Ammeter?

Hi

Yikes.... what a lot of questions!

Go through what I have already posted and see how many I have already answered then filter them out of this list.

For things like noise, if you want 22Hz to 22KHz filtered measurements you are going to need more test gear... my first point in my previous post.

[Walters]

Geoff

What test equipment do i need then ?


How to measure the overloading of an input?


Current draw of the power supply?


Testing for noise ? I know there is a noise meter do i need that?


What about for time measurements? for clocks? how do i do that?


Do i need a frequency counter?

[Tim Farrant]

Walters, stop taking the piss with us. If you seriously want to find out how to do all that stuff, take a course in electronic engineering like everybody else. You know as well as I do that all those questions cannot be answered on a message board - you gotta take a practical course man! tutt tutt

I got a question for you - where are you from?

Tim

[Walters]

Why whats the problem with the questions?

[tINY]

The problem is that you ask the questions like someone who doesn't even know what you want to accomplish or know. Some of the questions are asked twice and some of them don't even make sense....

If you want to know about audio measurements, go to the Liberty Instruments website and look at the Praxis info.



-tINY

[Tim Farrant]

Originally Posted by Walters

Why whats the problem with the questions?

The problem is, they cannot be answered within the confines of a message board. It would take someone a week to write a reply. I am not suggesting you are wrong to have those questions, although I do wonder if you are just taking the piss.

How about telling us a bit about yourself?

Thanks
Tim

[Walters]

Can't someone just say in a nutshell or simply it ?

[toolskid]

and tim hits the nail on the head with:

how about telling us a bit about yourself?

go on walters - hows about a little bit about yo bad self...

[Geoff_T]

Originally Posted by Walters

Can't someone just say in a nutshell or simply it ?

Walter

With all due respect to your desire to learn... and I could answer all your questions in depth... you need to learn some ettiquette.

It took me about 15 minutes to type my original response that I wrote in terms that a non-tech ought to be able to understand.

The next response you should have said was "thank you".

Call me old fashioned but that's kind of an expected response...

Instead you bombard me with more questions, some of which repeat previous questions that I already answered.

As Tim pointed out, you really need a better grounding in electronics as it seems that you don't fully understand what you can do with your existing test gear. You would be better off going on a evening class course or buying a text book or two if you really need the amount of tech help you imply by the number of questions you bombard the board with.

One question at a time would be less selfish...

[Walters]

Sorry Geoff i thought you could answering them at your own time you
didn't need to answer all right away just take your time

[Geoff_T]

Originally Posted by Walters

Sorry Geoff i thought you could answering them at your own time you
didn't need to answer all right away just take your time

Hi Walter

A lot of the questions you ask border rhetoric if you have an oscilloscope and know how to use it.

Back in the 1960's I had a cheap multimeter (analogue... digital meters used nixie tubes back then and cost a fortune) and I decided I needed an oscilloscope if I wanted to do any serious electronic projects.

I had the choice of buying huge government surplus scopes for relative peanuts
http://www.thevalvepage.com/testeq/cossor/1049/1049.htm
but they were huge and weighed about 100lb (and only 100KHz bandwidth). I wanted something that would fit on the bench I had!

That's when I spotted the Heathkit Oscilloscopes that were available as kits back then. For 23 pounds, 18 shillings I had me a little service scope kit and, being a kit, it was excellent soldering practice. It worked the first time I turned it on, I still own it and it still works... though I don't use it for anything now... it's on a shelf with a bunch of other vintage Heathkit gear.

Why did I buy an oscilloscope?

Because you can study the waveform visually to see what effect your circuit has on the signal. I had a Japanese (Eagle) tube based oscillator and, if I fed a sine wave signal into a circuit and the output had flattened top and bottom... I knew that I had a headroom/overload issue. I could put the scope probe at different places on the circuit and see where the distortion started.

You can also measure voltage and frequency.. the latter two ways. Either by working it out from the time base of the oscilloscope (as I detailed in the first reply) or by using Lissajous patterns. If you don't know what they are, do a web search... eg http://www.egr.msu.edu/classes/ece48.../lissajous.htm

You can see that you can use these wave forms to check the phase shift (hint, hint!)

You can even get a good idea of distortion because if the sine or square wave looks like crap... you know you have a problem.

A lot of your questions you could answer yourself by just poking about a known working circuit with the 'scope probe. I've given you all the info you need to get started.



PS I'd like to know a bit about you also... like where are you based? What do you do to earn a crust? Do you have your own studio? etc.