I’ve only used the Oscilloscpes and Function Generators at my university (big expensive Agilent machines) but I need to do some micro-controller work from home and purchased this scope/generator combination. The generators at my university had 50 ohm output resistances (like the PCSGU250) and the scopes were designed in such a way that they “assumed” a 50 ohm load resistance would be present, so the wave actually created by the generator had twice the amplitude set by the user. The idea being that the load circuit would create a voltage divider that would give the load circuit very close to the requested voltage levels. The PCSGU250 doesn’t appear to do this. Is this correct? So if I connect both the scope and generator to a 50 ohm resistor I should expect to get half of my deisired voltage. This is the behavior I’m seeing, I just want to see if it gels with what is expected by people more familiar with this specific equipment. If this is the case then I could be in trouble. I need to provide 0-3.3V waveforms to a micro-controller. When connecting that circuit to those other generators I mentioned I get the expected results so the load resistance is on the order of 50 ohms. I would expect that to get my 3.3 V wave form from this scope I would need a 6.6 V setting. But I can’t go higher than 5 in the software. Any advice on how to proceed would be appreciated.
I’d also like to know what the difference between high, low, amplitude, and max, min, peak-to-peak are in the waveform parameters screen. Shouldn’t some of those be the same thing?
In general is there an “advanced users manual” that describes some of the more complicated bits of the software (function generator fine tuning for example)?
[quote]… so the wave actually created by the generator had twice the amplitude set by the user.
The PCSGU250 doesn’t appear to do this. Is this correct?[/quote] Yes, the output voltage of the PCSGU250 is specified for open load or >600 ohm load.
Here: velleman.eu/products/view/?id=377622
is specified:
[color=#008000]•function generator:
◦amplitude range: 100mVpp to 10Vpp @ 1KHz// 600ohm load / 0V offset [/color]
There is a solution:
Just set the amplitude to 6.6V and the offset to 3.3V.
With 50 ohm load you’ll get 0-3.3V waveform.
[quote]I’d also like to know what the difference between high, low, amplitude, and max, min, peak-to-peak are in the waveform parameters screen. Shouldn’t some of those be the same thing?[/quote] Yes, in some cases.
Here’s a snippet from the oscilloscope Help file:
[quote]In general is there an “advanced users manual” that describes some of the more complicated bits of the software (function generator fine tuning for example)?[/quote]I’m sorry - no “advanced users manual”. You may use the Help for the oscilloscope and for the function generator.
In the Function Generator Help there is written about the fine tuning:
[color=#008000]Fine Tune - Allows to set a +/-7% level adjustment to the output voltage and +/-120mV adjustment to the offset voltage when the square wave output mode is selected. [/color]
When I posted that earlier question the software wasn’t allowing me to increase the output above 5 V. I’d type in 6.6 and it would change itself to 5. I had assumed that was intended functionality. The software is no longer doing that. But a belated thank you for the assistance. I have a new question. I’ve set up a basic test circuit, the function generator connected a 50 ohm resistor, and the oscilloscope across the resistor as well. Now that the software is cooperating I output a 6.6 V sine wave with 3.44 V offset at 500 hertz and read in a 3.44 V peak-to-peak wave. But if I change the output frequency to 2000 Hz I only read a 2.88 V peak-to-peak error. That is a chage of about 16 %. What is the reason for this discrepancy when nothing except the output frequency has changed?
