AndrejaKo, you read it with a more attention than me.
Sure the choice btw 50 Ohm or 1MOhm input is fine but the only the AC operation with 50 Ohm is strange.
TomC, what curve tracer do you have?
It looks interesting.
Hydrawerk, personally I don't agree with your statement.
I have almost 10mV improvement after some modifications to AOZ1094 circuit.
Here is the measurements that I had before.
The Average noise (16) at Acq. Mode is 22mV with 100us and 14-16mV with 500us (before 30-34mV)
The Sample (normal) noise at Acq. Mode is 32-40mV with the most to be btw 34-38mV (before 40-52mV).
The Peak noise at Acq. Mode is 32-44mV with the most to be btw 34-40mV (before 40-52mV).
The last attachment photo is what I do to adapter board.
I have almost 10mV improvement after some modifications to AOZ1094 circuit.
Here is the measurements that I had before.
The Average noise (16) at Acq. Mode is 22mV with 100us and 14-16mV with 500us (before 30-34mV)
The Sample (normal) noise at Acq. Mode is 32-40mV with the most to be btw 34-38mV (before 40-52mV).
The Peak noise at Acq. Mode is 32-44mV with the most to be btw 34-40mV (before 40-52mV).
The last attachment photo is what I do to adapter board.That's excellent!
With that low average noise you shouldn't have any problems triggering on low level signals!
Recently I was checking the GND noise on my scope with the ferrites on the probes which I now have permanently installed, on sample mode, the noise is no longer strong enough to allow me to trigger the scope (normal trigger) anymore.
I will soon start testing my old PSU, I've been preparing the test bed, and that includes better means of testing at mains voltages from 100-250VAC. So I'm in the process of redesigning my variable AC supply to include that facility.
I have almost 10mV improvement after some modifications to AOZ1094 circuit.
Here is the measurements that I had before.
The Average noise (16) at Acq. Mode is 22mV with 100us and 14-16mV with 500us (before 30-34mV)
The Sample (normal) noise at Acq. Mode is 32-40mV with the most to be btw 34-38mV (before 40-52mV).
The Peak noise at Acq. Mode is 32-44mV with the most to be btw 34-40mV (before 40-52mV).
The last attachment photo is what I do to adapter board.That's excellent!
With that low average noise you shouldn't have any problems triggering on low level signals!
Recently I was checking the GND noise on my scope with the ferrites on the probes which I now have permanently installed, on sample mode, the noise is no longer strong enough to allow me to trigger the scope (normal trigger) anymore.
I will soon start testing my old PSU, I've been preparing the test bed, and that includes better means of testing at mains voltages from 100-250VAC. So I'm in the process of redesigning my variable AC supply to include that facility.
The one day I was happy the other day was unhappy!
Now, I have problem with the measurement by long gnd lead.
Look at the attachment captures.
With the short gnd clip everything is OK but with the long gnd lead everything is bad.
Now I must looking what went wrong...
The signal is clearly from noise but has oscillation.
TomC, at page 107 you have done the same test and you were OK.
At the same time I have done the same tests until 10MHz (I have 10MHz signal generator) and I was OK, too.
I changed the L2, I removed the second L and bridged this, I removed the smd capacitor next to D127, I removed the zero resistor btw the two ground planes and bridge this...but nothing! The same issue is continues...
TomC, at page 107 you have done the same test and you were OK.
At the same time I have done the same tests until 10MHz (I have 10MHz signal generator) and I was OK, too.
I changed the L2, I removed the second L and bridged this, I removed the smd capacitor next to D127, I removed the zero resistor btw the two ground planes and bridge this...but nothing! The same issue is continues...
TomC, your suspect that part of the problem is the resonance of the ground lead and the probe's input capacitance, probably is true but I have the suspection that to me there is adding problem.\
I add some ferrites to the probe, nothing the same.
I change the generator frequency from 4-10.9MHz nothing the same.
From what I see there is a ringing to all frequencies.
Look at the attachments. At the first I connected the probe to signal generator output with ac mains off....what is this?
If I turn the switch on of the signal generator I have always the same ringing (see at the 4.1MHz), if I lower the amplitude of signal generator until very low the signal will be the same like complete closed!
I use two ferrites on each probe, the type that you normally use for power cables, one near the BNC, and the other near the probe. The probe cable is looped once around each of these ferrites for double the inductance
Lemon,
Here are some captures at the frequency that looks worst on my scope, on the first two there are no ferrites on the probes and the probes are hanging down. The third capture is with the same settings but I have re-installed the ferrites on the probes. I don't think these signals are that different from what you got. I still suspect that part of the problem is the resonance of the ground lead and the probe's input capacitance. I don't remember for sure, but is possible that when I did the tests on page 107 I had already permanently installed ferrites on my probes. I tried to get those results again without the ferrites by positioning the probes differently and couldn't in the frequencies around 10MHz. When I get to around 20MHz the 100MHz ringing mostly disappears. It is worst at the frequency of the attached images.
I done one measurement of 10MHz at 40mV output. Two large ferrites with each of them with one looped cable inside.
Yes there is an improvement but without right triggering. The reason of this is that I have removed all the mods to the Led Back-light Circuit and for this time the gnd-noise has increased.