function generator - need advice

[ChrisA]

Are you only working in the audio range? Id so then you can use a good quality audio interface. Software can send any kind of tone you like, sine wave, square or whatever. The better USB or Firewire interfaces are very good quality, good enough for use in recording studios.

If you need more power then connect the interface to an audio amp.

Using a multi channel audio interface you can send a sweep function to the device under test and use two input channels to measure voltage v. time at input and output.

 

[shuang]

I don't want a computer involved in the solution, although I am fairly computer software/hardware literate.

I just want an answer to my specific questions about the dedicated sine wave generators (with very low distortion) mentioned in my last post.

 

[Stefanoo]

Shuang,

I haven't undestood very well whether you are looking for a very low distortion signal generator or not.
In one of my previous post I said I am possibily going to resell my SoundTechnology ST1410A which features 0.001%distortion on all the audio band 0.002% at 100KHz with filter on.
Also features Intermodulation Signal for IM analysis.

Let me know.

 

[shuang]

Shuang,

I haven't undestood very well whether you are looking for a very low distortion signal generator or not.
In one of my previous post I said I am possibily going to resell my SoundTechnology ST1410A which features 0.001%distortion on all the audio band 0.002% at 100KHz with filter on.
Also features Intermodulation Signal for IM analysis.

Let me know.

Yes. I am looking for a low distortion sine wave generator but want to pick it up locally from a company I deal with and who can calibrate/service it. Also something a bit more common.

Thanks anyways.

 

[Stefanoo]

ah ok...no problem....

yes it is not a common part I do agree with you.
I actually wither way like to keep it.
Just for reference, I have the service manual and calibration is it really easy as long as you have a precise multimeter and frequency counter.

I do have a very precise one so it was super easy to fine calibrate it and does work really well I have to say.
I'd suggest it to you if you find one on a local company

 

[shuang]

I guess I would also be interested in a good hand held LCR meter for measuring the various properties of the cables as well.
What is a LCR Meter?

I would probably pick this one up new. Perhaps from a supplier like Newark.
Search Results | Newark.com

I have been told to get a unit which negates the contribution of the test leads.

Thanks for any suggestions. Price range from $52.95 to $331? Not sure the benefits as price increases.

 

[Stefanoo]

Sorry, but if you can't understand what the benefits are by going up with the price ehehehe....

hhhummm!!! First of all you want to decide for your self your maximum price range....and you are good $330
Second and probably the most important is set the precision and resolution you need.
The more the precision the more the price.

Now if you want to measure proprieties of the wire I don't think you can go for a low precision one and I highly doubt you can find one for that price...ususally they go way over $1K.
But if you look for a 0.3% precision or so...I'd suggest the same one I am looking at now...since I would like to get a LCR with a decent precision


but it is not definitely from a local pick up...ehehehe


LCR meter TH2821B measure inductance, capacitance and R - eBay (item 300401719725 end time Apr-28-10 19:34:31 PDT)

 

[shuang]

But if you look for a 0.3% precision or so...I'd suggest the same one I am looking at now...since I would like to get a LCR with a decent precision
LCR meter TH2821B measure inductance, capacitance and R - eBay (item 300401719725 end time Apr-28-10 19:34:31 PDT)

The price looks good.

This unit has 100hz, 120hz, and 1khz test frequencies. For testing audio cables how important is it to also have higher frequencies, i.e. 10khz and 100khz.

Also is it useful to purchase the optional TH26027 4 terminal Kelvin test clip leads to negate the contribution of the test equipment leads in the measurements?

 

[ChrisA]

The price looks good.

This unit has 100hz, 120hz, and 1khz test frequencies. For testing audio cables how important is it to also have higher frequencies, i.e. 10khz and 100khz.

Also is it useful to purchase the optional TH26027 4 terminal Kelvin test clip leads to negate the contribution of the test equipment leads in the measurements?

Depends of what you are testing for. To measure very small values of L and C you need to test at the higher frequencies. The way the measurement is made is that they really measure reactance and small reactance is harder to measure.

The four lead test clip is so that you can make accurate measurement of low resistance devices. You do need this for low DCR measurements so that no current flows in the test leads

 

[shuang]

Depends of what you are testing for. To measure very small values of L and C you need to test at the higher frequencies. The way the measurement is made is that they really measure reactance and small reactance is harder to measure.

The four lead test clip is so that you can make accurate measurement of low resistance devices. You do need this for low DCR measurements so that no current flows in the test leads

Since I will be primarily doing measurements with cables I am thinking of the following ranges (a factor of 10,000), with optimal accuracy.

Resistance
0.001 ohm to 10 ohm

Inductance
0.01 uH to 100 uH

Capacitance
1 pF to 10,000 pF

This is within the range of the meter Stefanoo recommended. That meter has 100hz, 120hz, 1khz frequencies selectable.

Is that frequency range adequate for cable measurements. Most audio cable vendors do not specify the frequency that the measurement are taken at. Kimber is the exception and specifies that the measurements are taken at 20kHz.

The more expensive meters will provide 10khz and even 100khz frequencies.

Should I at least look for a meter which supports 10khz?

Here is an example where someone took the measurements at different frequencies.
Measuring Cable LCR ParametersMeasuring Cable LCR Parameters - Audioholics Home Theater Forums

He used a B&K 885 LCR meter which has settings for 100/120/1khz/10khz frequencies.