Products > Test Equipment
Siglent SDS804X HD - No USB Power From Scope ? *Got Power But Trips Port*
TomKatt:
I recently procured a Micsig DP10007 Differential Probe (older model) that requires a 5V USB power source. I assumed that one of the two USB jacks on my SDS804X HD scope would work as a power source for the probe, but it fails to run when plugged into either USB jack on the scope. The probe powers up correctly when plugged into a USB AC adapter. The probe spec sheet indicates it only requires 1.25W of power, so I can't believe that the USB jacks on the scope are limited to less than that. I tried two different USB cables and neither worked with the scope.
I know the USB ports on the scope work as I have used usb drives to transfer files and update the firmware and did not encounter any issues.
Is there a 100ma power limit on the scope USB ports? 1.25W should only be about 250ma, which I would have expected to be sufficient.
EDIT - After testing again with a thumb drive, initially the drive was not detected. I power cycled the scope at which point the usb drive was detected and I was able to browse the drive through the file manager on the scope. I then swapped the thumb drive with the differential probe and it powered up normally.
Very strange.
TomKatt:
There's definitely something wonky going on here - not sure how I managed to get the probe to power up once, but now every time I plug the probe into the scope it fails to power up. Occasionally I can see the trace drop in cycles as though the probe is attempting to fully power up, but it never does. Once I plug the probe into the USB port for power (and it fails to power up), if I then plug the thumb drive into the scope it does not detect it any longer. Power cycling the scope appears to reset the USB port and the thumb drive is once again recognized. But as soon as I plug the probe into the scope it's as if the probe trips some current limit and it seems to shut down the USB ports until the scope is power cycled.
For now, I'm going with the premise the the Micsig DP10007 probe requires more current than the scope can provide. That still seems odd as I believe I have seen numerous videos of this probe being powered by scopes online. I have an SDS1104X-E at work and I'll try this probe on that scope tomorrow.
EDIT - I always wanted to get one of those cheap USB power analyzers anyway... I'm very curious how much current this differential probe draws... There's not much to it - I'd be surprised if it took more than the 500ma USB 2.0 is rated for.
tautech:
--- Quote from: TomKatt on July 16, 2024, 09:05:35 pm ---There's definitely something wonky going on here - not sure how I managed to get the probe to power up once, but now every time I plug the probe into the scope it fails to power up. Occasionally I can see the trace drop in cycles as though the probe is attempting to fully power up, but it never does. Once I plug the probe into the USB port for power (and it fails to power up), if I then plug the thumb drive into the scope it does not detect it any longer. Power cycling the scope appears to reset the USB port and the thumb drive is once again recognized. But as soon as I plug the probe into the scope it's as if the probe trips some current limit and it seems to shut down the USB ports until the scope is power cycled.
For now, I'm going with the premise the the Micsig DP10007 probe requires more current than the scope can provide. That still seems odd as I believe I have seen numerous videos of this probe being powered by scopes online. I have an SDS1104X-E at work and I'll try this probe on that scope tomorrow.
--- End quote ---
This.
Normal behaviour for a heavy USB load at boot.
Try other USB powered devices as you might find a sweet spot that when exceeded shuts down USB supply when booting.
IIRC after boot, 500mA was the trip point.
Martin72:
Hi,
It sounds to me that the differential probe has an inrush current that is too high (for the scope).
The differential probe contains switcher circuits that process other voltages from 5V and these switcher supplies could have an initially “high” inrush current.
This will be very short, but possibly too long for shutdown detection.
TomKatt:
Yes, both these replies align with my thoughts as well. I powered the probe from my Siglent SPD1305X linear power supply and although the display isn't quick enough to display the inrush current, it hits 219ma (1.095W @ 5V) almost immediately. So there must be some caps getting charged in the probe at power up that push things over the limit. I'm a bit surprised that this is enough to trip the scope ports, but I guess I'd rather they are well protected instead of something damaging the more expensive scope.
Thanks for the input! I should run the power through my multimeter set to peak ma just to satisfy my curiosity...
Navigation
[0] Message Index
[#] Next page
Go to full version