FeelTech / FeelElec FY6800 Amplitude - Page 1
Forum section: electronics / testgear

author: ScottW
author_rank: Contributor
timestamp: September 07, 2021, 01:49:43 am
content: I'm confused by the output voltage I'm seeing from my FY6800.The FY6800 spec sheet says amplitude at <10MHz is "1mVpp-20Vpp" into 50 Ohms.So I set the FY6800 for 1MHz sine and 10V, and connected itdirectlyto my SDS1104X-E (no terminator, just a 24" straight coax). The 1104X-E has only a 1M mode, no internal 50 Ohm mode. So I *expected* to see double the voltage of the FY6800's setting, or about 20V peak-to-peak. But no... The scope showed 10V peak-to-peak.If I add an external 50 Ohm terminator, it does of course cut the voltage in half. But then a setting of 10V on the FY6800 shows up as about 5V on the scope (i.e., half the FY6800 output setting).Is the FY6800 spec sheet wrong about the 50 Ohm output rating? Or am I just expecting the wrong behavior?

author: rf-loop
author_rank: Super Contributor
timestamp: September 07, 2021, 04:16:03 am
content: Quote from: ScottW on September 07, 2021, 01:49:43 amWhere it is told exatly "10MHz is "1mVpp-20Vpp"into 50 Ohms."Its source impedance is 50 Ohm +/-10%Output voltage is not specified to 50 Ohm load. It is specified for open (Hi-Z) load because it do not tell load at all.Least here:http://en.feeltech.net/index.php?case=archive&act=show&aid=61

author: ScottW
author_rank: Contributor
timestamp: September 07, 2021, 04:53:45 am
content: @rf-loop, Thank you for the reply. Greatly respect your knowledge, but I don't understand what you are telling me about this FY6800.From the link you posted:Output Characteristics section says Amplitude at Freq <=10Mhz is "1mVpp - 20Vpp"Waveform Outputsection says "Impedance 50 Ohms(+/- 10%) Typical"Doesn't that second item mean the specified output voltages are into 50 Ohms?I am not knocking the equipment, but rather am just trying to understand what I should expect and am confused by the results.

author: bob91343
author_rank: Super Contributor
timestamp: September 07, 2021, 05:33:56 am
content: The specification doesn't state what you want to know. The output voltage has a source impedance of about 50 Ohms but it doesn't state under what load you measure the amount they say.I don't think they are trying to hide anything but there is a language barrier that is causing the confusion.

author: ScottW
author_rank: Contributor
timestamp: September 07, 2021, 05:52:08 am
content: So should I be interpreting the FY6800 spec as saying output voltages are with no load?Again I’m not knocking the fy6800 but just trying to understand what to expect.Am I correct in thinking it is “typical” for signal generator output voltage specs to be stated with 50 Ohm load? Is the fy6800 atypical in this respect?

author: rf-loop
author_rank: Super Contributor
timestamp: September 07, 2021, 06:09:10 am
content: Quote from: ScottW on September 07, 2021, 04:53:45 amNo, it just tell it comeout from50 Ohm impedance, aka its Waveformoutput impedanceis 50 Ohm +/- something. as they say. It is much better if they clearly say it for avoid confusions. They tell it only in Output specifications so it mean just Output connector. But good practice is they tell in Output characteristics that these values are without load aka Hi-Z.QuoteExample how other manufacturer tell it (here Siglent)(I have simplified it removing some non relevant info for this topic)QuoteAnd user manual explain it further.

author: rf-loop
author_rank: Super Contributor
timestamp: September 07, 2021, 06:17:05 am
content: Quote from: ScottW on September 07, 2021, 05:52:08 amSimply. Yes.

author: ScottW
author_rank: Contributor
timestamp: September 07, 2021, 02:45:58 pm
content: Got it.Thank you for the explanation!