Signal generator

[patroclus]

Hi!

I'm looking for any used signal generator. But I only worked with one in university, and I'm not much into the specs.

I know some signal generator which have a 50ohm output, others have 600 ohm. 50ohm should be much better, in theory.
Also, some of them can output a variable amplitude signal between 0 and 3, 0 and 10 volts, etc... other have a DC offset, for example, 10V with 600ohm load, and 5V offset. I suppose this is worst, because you can't get 1,5V, for example... only some values are possible. For example, with a 600ohm load, only 5 to 15V would be possible.

I really don't know what to choose, but if you can give me some advices, I'll be thankful

 

[Nigel Goodwin]

Perhaps you might mention what it is for?, audio?, RF?, function generator?.

 

[patroclus]

Sure

General electronics. Function generator. To test circuits with oscilloscope.
Not for audio or RF for now, though audio would be nice in a the future.

My main concern is weather to choose a 50ohm output or a 600ohm would be fine.
As I'm reading now, most generator have a maximum peak to peak output at OC, but appart from DC offset, they include a variable attenuator, so you can get very low signals. So that would be fine.

 

[Optikon]

Sure

General electronics. Function generator. To test circuits with oscilloscope.
Not for audio or RF for now, though audio would be nice in a the future.

My main concern is weather to choose a 50ohm output or a 600ohm would be fine.
As I'm reading now, most generator have a maximum peak to peak output at OC, but appart from DC offset, they include a variable attenuator, so you can get very low signals. So that would be fine.

Get one with 50 Ohm output. The 600 Ohm stuff is much more specialized.
Also nice to have:

1) Trigger input
2) Output range +/-10 V
3) Frequency of all functions at least 1MHz, 10MHz = much better.
4) VCF / sweep input so you can set the output frequency by applying an input voltage. This is good for making poor-man bode plots with a scope.
5) If you really want to get value for your $$$ buy from a reputable MFG. If you get a hong-kong special or some put it together yourself kit, dont expect good specs and dont expect longevity.

 

[patroclus]

I thought 600 ohm was for the same purposes as 50 ohm, but 50 ohm is better because it delivers better voltage to the same load.

 

[Hero999]

The output impedance is only important when at higher frequencies when you want the source to match the transmission line.

A signal generaator with an output impedance of 50hm: will produce a perfect squarewave when connected to your scope via a piece of coaxial cable while an oscilloscope with a 600hm: output will distort the waveform when it's driving a 50hm: cable.