GW Instek MFG-2000 Newbie question

GW Instek MFG-2000 Newbie question
Posted by Agosto on 18 Apr, 2024 17:33
I just acquired a used GW Instek MFG-2130 Function Generator. All went well during initial setup until I tried to enter a specific amplitude for a desired sine wave output: When I key in an amplitude of 100mV RMS, I measure at the output 202mV RMS (measured with 3 different meters). When I press the various function keys at the bottom (e.g. "RMS, PP", etc), the amplitude value changes on the display (e.g. 100mV RMS changes to 282mV PP), but the output voltage remains the same. "200mV RMS" on display gives me 410mV RMS at the output.

Am I doing something wrong here or is there a problem with the function generator?

Thanks for any assistance

#1 Reply
Posted by nctnico on 18 Apr, 2024 17:41
Read the manual about the load setting. This can typically be set to high-z and 50 Ohm. This setting determines the scaling of the displayed amplitude. You probably have it set to 50 Ohm load while you have a high impedance load attached.

#2 Reply
Posted by KungFuJosh on 18 Apr, 2024 17:44
Yup, sounds like mismatched load. That will happen trying to connect any AWG to a DMM. You can test on your oscilloscope and see if it makes more sense (still needs to be properly loaded).

#3 Reply
Posted by Agosto on 18 Apr, 2024 17:49
Thanks to both of you! Yes, I read the manual but while changing the load parameter I was focusing on the output and not on the generator display. So indeed the displayed value doubles in "High Z" mode.
Now: After changing the load to "High Z" generator display shows 300mV rms, output is 308mV rms. Is the accuracy appropriate for a generator in this price range?

#4 Reply
Posted by KungFuJosh on 18 Apr, 2024 18:09
Quote from: Agosto on 18 Apr, 2024 17:49
Thanks to both of you! Yes, I read the manual but while changing the load parameter I was focusing on the output and not on the generator display. So indeed the displayed value doubles in "High Z" mode.
Now: After changing the load to "High Z" generator display shows 300mV rms, output is 308mV rms. Is the accuracy appropriate for a generator in this price range?

Accuracy should be stated in the spec sheet. However, is the meter calibrated and in spec also? If you only test with one piece, it's hard to know which one is telling the truth.

#5 Reply
Posted by Agosto on 18 Apr, 2024 18:13
Agreed. I tested with 3 different meters, analog and digital (including scope). Could not find the accuracy in the specs, will check again. Thanks