Help to choose an economic Function Generator with two to three decimal places - Page 1
Forum section: electronics / testgear

author: kavehm
author_rank: Contributor
timestamp: February 14, 2023, 10:24:14 pm
content: I need an economic function generator with an accuracy of two to three decimal places and frequency stability and no frequency change up to the range of 2MHz.In the videos I saw on YouTube, the function generators does not have a fixed output and the frequency is constantly changing.Those who have experience working with the function generator, I would be grateful if they could guide me.Thanks,

author: nctnico
author_rank: Super Contributor
timestamp: February 14, 2023, 11:28:00 pm
content: Search the forum for Feeltech and Uni-t function generators. These will very likely fit your needs. The videos you've seen are likely showing older function generators which are RC oscillator based and those drift all over the place. Not worth buying nowadays.

author: kavehm
author_rank: Contributor
timestamp: February 15, 2023, 07:55:07 am
content: Thanks for your reply,I saw many reviews of different function generators. But none of them had a stable output when connected to an oscilloscope. For example, in a review of the Uni-T model UTG962e, when set to 5Hz, the output displayed by the oscilloscope was between 4.95Hz and 5.03Hz. In none of the models that I saw, they did not have a completely accurate output even at low frequencies.Do all the low-priced models have approximate output and only the expensive models like Keysight have fully accurate output?I need a model that can have accurate and stable output up to two to three decimal places. For example, when I set the output to 4500.25 Hz, the exact output is this frequency.

author: Someone
author_rank: Super Contributor
timestamp: February 15, 2023, 08:44:33 am
content: Quote from: kavehm on February 15, 2023, 07:55:07 amWhat was the specification for the frequency measurement? or the noise in that? UNI-T specify:Quote from: UNI-T UTG900E DatasheetI'd trust the manufacturer specification over some quick measurement.

author: Anthocyanina
author_rank: Frequent Contributor
timestamp: February 15, 2023, 08:52:44 am
content: Quote from: kavehm on February 15, 2023, 07:55:07 amThe specification of the UTG932e/962e claims +/-50ppm frequency accuracy, so for your 4500.25Hz example, it could be(within 90 days) between 4500.475Hz and 4500.025Hz.What you saw on that review is likely the oscilloscope counter having trouble with such low frequencies, and not necessarily the generator itself.I don't have the uni-t generator, but with the generators i have, i see the last digit flip depending on the oscilloscope i use to measure them.What is your application that needs such frequency accuracy and precision? could you share the video review of the generator you saw?

author: nctnico
author_rank: Super Contributor
timestamp: February 15, 2023, 09:48:36 am
content: Quote from: kavehm on February 15, 2023, 07:55:07 amThat is because an oscilloscope is the wrong instrument for doing accurate frequency measurements. A frequency counter is for measuring frequency, not an oscilloscope.

author: Fungus
author_rank: Super Contributor
timestamp: February 15, 2023, 03:27:22 pm
content: Quote from: nctnico on February 15, 2023, 09:48:36 amSome oscilloscopes have a built-in frequency counter which is more accurate than the number shown under "measurements".

author: kavehm
author_rank: Contributor
timestamp: February 16, 2023, 01:31:02 pm
content: Thanks for your guidance,The problem is that the oscilloscope is not a suitable device for frequency counting and a frequency counter should do this. Oscilloscopes have an option called a frequency counter that should be used.Keysight company has explained this issue in a video:Frequency Counter vs. Oscilloscope Frequency Measurements:

author: J-R
author_rank: Super Contributor
timestamp: February 16, 2023, 08:55:42 pm
content: It's true that even a cheap frequency counter from decades ago can easily give you 8, 9, 10 or more digits, but there are plenty of scopes that can reach 5 or 6. A cheap Owon scope I have is dead-on stable for all 6 digits no matter what I feed it from my GPSDO. So to say the scope is not suitable is just not correct unless more context is applied with additional requirements you may have.Furthermore, a common task with a scope is comparing a known and unknown signal by triggering on one and adjusting the known until it matches the unknown. Unknown = known.So maybe it's more correct to say some scopes can do this better than others, but a frequency counter is a good thing to have on your bench as well, preferably one with a good oscillator.