#137: Why your Function Generator's output voltage reading can be wrong

This video reviews the two most common reasons why the output amplitude setting on a function or signal generator doesn't match what is read on an oscilloscope. This can be due to an incorrect attenuation setting on the scope, but is most commonly due to the fact that the generator is not presented with the load impedance that it is expecting. To correct this most common case, you can either use the correct load impedance, or tell the generator what load you are presenting it with.

[mariofilippi]

Ran into this problem many times. Lots of head scratching trying to figure what's wrong. You had the answer. Thanks OM.

[cencalgrizz]

I'm currently studying Electrical Engineering and have had this issue in labs. The TA that was instructing just chocked it up to the signal generator just not being very accurate. I'm glad you set the record straight.

[NivagSwerdna]

Just ordered my first signal generator.... and I think you just saved me from my first confusion! Thx

[RobB_VKES]

Oscillator LOL. Hope the Cold clears up soon
Abasinia

[NagoyaT]

Alan -- you make everything so clear. Thank you for this and all your other videos.

[BerettaDan]

Thank you, Alan. I really appreciate your taking the time to send me an answer. I need to go back to your earliest videos and do some catching up! Best wishes...Dan

[marcusjenkins]

Great vid. Sounds like a very sore throat, so extra thanks for battling through. Get well soon! 73's, EA5IGC

[erickapilik]

Thank you for explaining the purpose of the High Z option. You made that simple.

[nlimchua]

For a split second, I thought I was watching a diff't channel. You sound diff't - it's allergy season here in NJ! Hope you feel better. Another good video.

[PersonaRandomNumbers]

Oh, wow. I had no idea that's what that was -- I've just been told to put the signal generator into high-z mode and not known why! Thanks for the information, it's incredibly helpful.

[gfvt]

Hi Alan, I have seen people tripped up by this before. A lot of old signal generators were marked "EMF" or "PD" to differentiate between the levels they would generate into Hi-Z or 50 ohms.
It can be frustrating with modern test equipment where the termination options are hidden in menus somewhere and not permanently displayed on screen.

[TonyButchT]

Invaluable information as always! Thank you!
Next request: Lock the door into the lab, rest up, get well!

[dennisbauer]

Well thank you so much again, was just wondering about this because was trying to measure impedance using sig gen and oscilloscope, so look on your channel and here you are, a lifesaver

[DAVET]

A timely and useful reminder. Thanks once again Alan.

[CollinBaillie]

I want to generate a "noisy dc" signal. Say a 5Hz 0v-5v primary and a 0.5v p2p 100Hz ripple on that 5Hz signal. How do I do that?

[ChipGuy]

Recently I went from an audio function generator to a real one (Agilent 33220) and was wondering why it showed double the value until I realized: "sure it has 50 Ohm in series and shows for 50 Ohms termination". So I just added a 50 Ohm terminator. Searched for a menu item on my generator to set it up properly, didn't find a menu item. You video made me look into the manual, and what do you know: Its not in the Output menu, it's in the Utility menu. That's Agilent for you ;) (Where files are not deleted but purged :))

[kodiakfitty]

Great video Alan. This brings up the question: how does one go about determining the input or output impedance of a circuit?

[Avionics]

Sir, as always you teach me something that i never knew, thank you,

[matthewdavis]

Thanks for being here, I need people like you.
73

[ovalwingnut]

Dial-in your desired impedance 😲 Sweet! 👍😁 Excellent vid. Thank you!