USB Oscilloscope Connection

Intona 7054 and 7055 series
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gronkle1972
Posts: 2
Joined: April 5th, 2022, 10:53 pm

USB Oscilloscope Connection

Post by gronkle1972 »

I have purchased 7055-D to use with a USB power Oscilloscope (PicoScope 4262). I am struggling to get the Oscilloscope to function and want to know if there is a check-list of options to try? The Oscilloscope appears in device manager when plugged directly into laptop, but doesn't appear when plugged in via 7055-D. There is some flashing on the light of the 7055-D but not sure what exactly the flashing is to correlate with 7055-D data sheet. The laptop is a Dell Precision 7510 and I believe all the USB ports are USB 3.0.

1) I believe the PicoScope 4262 is USB 2.0 powered and therefore the power is limited to 500mA, this should mean the 7055-D should be able to power without aux power supply?
2) Would any aux power supply be sufficient to try for secondary aux power options, if this worked do you have a recommendation of low output noise power supply?
3) Would using a USB C to the USB 3 type B connector make any difference?
4) Does the Laptop need to be plugged in for the correct voltage stability on output?

I am happy to have any other suggestions too.

gronkle1972
Posts: 2
Joined: April 5th, 2022, 10:53 pm

Re: USB Oscilloscope Connection

Post by gronkle1972 »

Following further testing I have got the Oscilloscope working, but not under ideal circumstances. With response to my points from the original post

4) With the laptop plugged in the oscilloscope flashed on and off in device manager indicating some problems with the connection, better than before
3) Changing to USB C made no difference despite the potential higher power available.
1) I added an aux power supply from a second USB socket on the laptop (I know completely makes the isolator redundant) but the oscilloscope started to work stable. I am yet to test with and isolated power supply but I suspect the oscilloscope drew more power than the 7055-D provided.
2) I am now searching for a low noise 5 V power supply which supplies more than the 500 mA the 7055-D provides. I think the 7055-D uses an LT3045 for its isolated power supply which is an exceptionally well specified voltage regulator for this job. My current intention is to try and build a linear power supply which uses a TPS7A91 (probably via the evaluation board TPS7A91EVM-831) which should be able to provide low noise and high PSRR up to 1 A.

Daniel (Intona)
Posts: 87
Joined: May 6th, 2020, 8:29 am

Re: USB Oscilloscope Connection

Post by Daniel (Intona) »

We happen to have a 4262 in the lab. Yes, you unfortunately need to power the AUX port to get this scope working well.
The typical noise out of a standard charging wall wart should not harm the performance of the scope in any way. (Hey, it's just 16 bits and the Picoscope preamp stage is very well designed)
We use medical grade supplies by Mean Well and Friwo (German brand). Anker is also very good, but suffers from extended isolation. No linear regulation, though.
1) I believe the PicoScope 4262 is USB 2.0 powered and therefore the power is limited to 500mA, this should mean the 7055-D should be able to power without aux power supply?
In theory. Unfortunately, the power of the isolator itself is added to what the PC sees and the thinny USB wiring finishes this off by dropping voltage down to 4.x volts.

I will make some tests here and come back to you in the next days.
Daniel (Intona)

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