BK Precision 4040 Func. Gen square wave question

[Beowulf]

Hi,
I purchased this item from ebay and I'm checking everything within the reach my limited knowledge. So far everything looks good but I have a question to ask anybody with a similar unit or anybody who understands this concern of mine.
So my concern is weather this unit is functioning properly when generating a square wave signal or if it needs calibration/repair.

Attached is the user's manual, plus pictures that show the "square waves" I'm getting on my scope.

As you can see when I go higher on the frequency, there starts to be some distortion.

I understand this could be normal, to some extent, due to harmonics on the oscilloscope etc.

So what are your thoughts?

Thx

[Kiriakos GR]

Re: BK Precision 4040 Func. Gen square wave question

I have made recently some training circles with the Twintex TFG-3620E arbitrary waveform FG.

Some distortion is natural effect when getting close to 60% of the full range of frequencies that your model can deliver.
The sampling rate of most FG is low, and in simple English all FG have sufficient sampling rate for perfect reproduction of signals up to 100Khz.
Above that 100 kHz the quality of the waveform starts to degrade, how much it does that.. it depends on the quality of the FG it self and their sampling rate.

You have also overshooting problem due impedance mismatch, the FG is 50 Ohm and the scope 1M Ohm.

[Beowulf]

Re: BK Precision 4040 Func. Gen square wave question

Thank you Kiriakos GR. Always appreciate your feed back.

[budm]

Re: BK Precision 4040 Func. Gen square wave question

This unit is Analog FG, no sampling involved. Are you trying to get the Sq wave output at at 20MHz? See the spec of the Sq out put freq.

[Beowulf]

Re: BK Precision 4040 Func. Gen square wave question

I had not seen or noticed the specs for the square wave (0.1 to 100khz), makes sense now. My first time playing with a function generator and thought it was supposed to produce a nice square wave up to the unit's rated 20mhz frequency.
Thanks budm.

[Kiriakos GR]

Re: BK Precision 4040 Func. Gen square wave question

Just of curiosity what is the duty cycle range?

Not even this BK specifications document have that info.

Edit:
In the user manual there one line saying about 15:85 (15%Low up to 85% Max)
If this is the range... is not fantastic but for the price I think that is good enough.

[Longbow]

Re: BK Precision 4040 Func. Gen square wave question

In the user manual there one line saying about 15:85 (15%Low up to 85% Max)

That is your duty cycle range. The peaking at the lower frequencies is due to X1 scope probes. You should be using a 50 ohm termination and a X10 probe to get a proper waveform on the scope.