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Guest
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 Posted: Thu Dec 16, 2004 2:33 pm Post subject: isolation pico 300o sries |
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| what kind of isolation has the picoscope 3204 between the gignal ground and the usb port? |
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Sarah
Guest
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| Posted: Fri Dec 17, 2004 10:47 am Post subject: |
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Hi
Thank you for your post.
There is no isolation between the signal ground and the USB port on the PS3000 series.
Hope this helps
Best Regards |
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ylo58
Active User
Joined: 11 Oct 2004
Posts: 8
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| Posted: Sun Dec 26, 2004 12:29 am Post subject: isolation pico 3000 sries |
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I have a related question:
if there is no isolation, then how is the external power supply supposed to help against ground loops?
Thank you in advance,
Ulo. |
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Guest
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| Posted: Sun Dec 26, 2004 8:57 pm Post subject: |
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The web site states:
"In normal operation the PicoScope 320x is powered either from a USB port on your computer or from a powered hub. It is not possible to power this device from an unpowered USB hub. If both the PC and the device under test are referenced to the same ground (earth) then noise/offset problems may occur. This problem is only likely to occur when using a mains powered desktop PC whilst measuring DC coupled (earth referenced) signals of a small amplitude. If this situation occurs a mains power adaptor (supplied) will have to be used to power the unit."
The scope is protected against overload / misconnection by self resetting fuses. Like most USB scopes powered from the PC an earth loop can be created in the above circumstances. Powering instead from the external mains power supply avoids the earth loop as the power now comes from a floating supply. |
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ylo58
Active User
Joined: 11 Oct 2004
Posts: 8
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| Posted: Mon Jan 03, 2005 4:42 pm Post subject: |
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Thank you for clearing this up. I would put it this way (in technical terms):
The external power supply eliminates the DC voltage drop in the ground wire of the USB cable, caused by the supply current. This can be a problem, especially because the supply current changes over time.
I would also be very grateful if someone could provide more detailed specifications of these self resetting fuses (something like the description
of their operation and connection diagram). It would be nice to know beforehand, when and why the box will kick me in the face. |
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Sarah
Guest
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| Posted: Wed Jan 05, 2005 9:56 am Post subject: |
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Hi
Thank you for your post.
For safety reasons, all varients of the PS320x have resettable 0.3A fuses between the grounds of the BNC connectors (please note however that some early PS3206 versions have non-resettable 10A fuses).
Unfortunately we do not provide a connection diagram.
Hope this helps
Best Regards |
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