Products > Test Equipment
Siglent1104X-E versus Square Waves
maddoxhq:
I was using a probe in the system when I was measuring the probes bandwidth yes.
When directly connecting the AWG to the scope earlier, no.
I picked the 50ohm terminator off the floor and tried again. Channel 1 has the terminator and a 1.5ft BNC cable, Channel 2 has only the 1.5ft BNC cable. And for funzies i set both channels to square wave to see if that made any difference.
And not really, the passthrough terminated side is still half the amplitude of the just cabled side. The square waves themselves are pretty much the same for the most part.
I would have expected what you saw though. Without the feedthrough, nearly double the voltage. The big thing here is I CANNOT change my AWG to HiZ mode. I grabbed up everything I could from the interwebs, including some dodgy Chinese software to interface with it. It's 50 ohms output impedance out of the box, or at least it says it is.
Headed to bed for now, the suns making its way to my neck of the woods.
807:
The Koolatron is rebadged under various names. It's output impedance is always 50Ω, but the displayed output is always HiZ. Unlike my Uni-T UTG962E it doesn't look like you can change the displayed output to represent 50Ω.
This means that if you were to look at the output of this generator on a spectrum analyzer, it would read half the displayed generator output. i.e. 2V p-p would read 4dBm rather than 10dBm.
See this video @ 5:37
https://youtu.be/b66nnWb3z54?t=337
BillyO:
A note on using a 50 ohm feed through terminator: You never use them with a standard scope probe. You only use them with 50 ohm transmission lines (straight trough 50 ohm cable) and with direct connect devices that require 50 ohm termination.
A note on standard scope probes: They always feed into a HiZ input. Never 50 ohms. The cable on a standard scope probe is not a 50 ohm transmission line. Not eve close. The generally have high resistance center conductors that will measure 300-500 ohms. If you use them with a 50 ohm terminator you will create a 1/7 to 1/11 voltage divider. This explains your 120mv signal from 1V at the generator
maddoxhq:
Sorry, tried to make this reply yesterday but the site wouldn't load.
--- Quote from: BillyO on August 10, 2023, 02:04:16 pm ---The generally have high resistance center conductors that will measure 300-500 ohms. If you use them with a 50 ohm terminator you will create a 1/7 to 1/11 voltage divider. This explains your 120mv signal from 1V at the generator
--- End quote ---
Now that makes sense to me, I wasn't aware there was such high resistance in the oscilloscope lead. Mine measures 335ohms. When it comes to the voltage divider are you just taking 50/(probe resistance + feedthrough impedance)?
BillyO:
--- Quote from: maddoxhq on August 11, 2023, 06:51:28 pm --- When it comes to the voltage divider are you just taking 50/(probe resistance + feedthrough impedance)?
--- End quote ---
Correct.
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