Hi,
I'm very proud of my new scope, been waiting 10 years!
Must say I'm disappointed LOL. I hope I just dont know how to use it....
I'm just trying to measure a frequency for cambridge audio cd6 VCO clock as per service manual states....Clock should 4.3218Mhz
I press auto and it finds the frequency, settings etc but the mhz is jumping around all over the shop!! Goes from 4.7xxx to 4.2xxx
Am I doing something wrong? should it jump around like that? I have attached service manual..
Would appreciate any advice......Oh its 100mv and 50.0ns as per service manual, not 100% on what that means but it matches up at least!
I'm very proud of my new scope, been waiting 10 years!
Must say I'm disappointed LOL. I hope I just dont know how to use it....
I'm just trying to measure a frequency for cambridge audio cd6 VCO clock as per service manual states....Clock should 4.3218Mhz
I press auto and it finds the frequency, settings etc but the mhz is jumping around all over the shop!! Goes from 4.7xxx to 4.2xxx
Am I doing something wrong? should it jump around like that? I have attached service manual..
Would appreciate any advice......Oh its 100mv and 50.0ns as per service manual, not 100% on what that means but it matches up at least!
I have another brand of Chinese scope (Owon) and the frequency measurement seems sensitive to the trigger threshold voltage. Try going to manual setting of the trigger threshold and vary it a bit.
Thanks...it's 4 am can't sleep..but will look into this.. manual mode I need to try and the trigger thing makes sense. When I adjust it the voltage goes up and down but really see much else happening.
It's a pretty advanced scope and does have some high pass and low pass filters apparently!
I'll send some pics tomorrow. Much appreciated
It's a pretty advanced scope and does have some high pass and low pass filters apparently!
I'll send some pics tomorrow. Much appreciated
Trigger level needs to be right. Half way up signal.
Make signal as big as possible on the screen.
Make signal as big as possible on the screen.
The VPLL 4,3218 is a hi jitter signal (nanoseconds level), so you must use a counter to ajust its. Or, use a single mode on dso, and marker for measurement.
You have a lot of noise on your squarewave, that's likely the reason for the frequency measurement to be unstable. Could the noise be mains hum? Check you have a sound ground connection at your probe.
How's the ground clip of the scope probe connected? If that signal is a square wave, you should see a clean square wave on the screen. What you have has a tremendous amount of noise or hum on it. That happens if you forget to connect the scope ground to circuit ground.
With high-speed signals you get better fidelity if you make the ground connection as short as possible. Often scope probes will come with a little bag of accessories, one of these accessories being a spring clip for the ground. Use it if you can.
Tom
With high-speed signals you get better fidelity if you make the ground connection as short as possible. Often scope probes will come with a little bag of accessories, one of these accessories being a spring clip for the ground. Use it if you can.
Tom
Perhaps if you had, say, 30 cycles of the waveform on screen - versus 3 - it would give a better frequency reading.
Smells a bit like an earth loop.
If scope and unit both are earthed then they might interfere with each other.
If scope and unit both are earthed then they might interfere with each other.
Sounds interesting but I have no idea how to do that!
Very basic understanding...I'm just trying to accurately measure the VCO and adjust it. But looks like I have to learn how to use a scope first which is definitely not easy! LOL