🚀 go-pugleaf

fang@phy.duke.edu (Fang Zhong) writes:


>	I work on small signals of less than micro volts.  I use a computer
>to control my experiment and take data via IEEE bus.  One of the equipments
>in my setup is a digial ratio transformer made my Eaton Advanced Electronics.
>This equipment was designed so poorly that a ten-times larger noise was
>added to my circuit if I added it to my IEEE bus.  
>	I would like to find a way to add the digital ratiotran to the IEEE
>while the noise is isolated only to the ratiotran.

>	Will an optical isolation work in my case?

Yes, but it is a pain to implement all those optoisolators.

Before you try something like that, note that your problems are most likely
due to a ground loop.  The IEEE bus has two ground lines, called "shield"
and "digital ground".  They shouldn't be hooked together anywhere, and your
instrument should not be using "shield" ground as its true ground.  Digital
ground should be the only ground that is connected between machines.  The
shield should be left unconnected unless you are sure all instruments have
their cases hooked to the power line ground, in which case it is safe to hook
shield to the instrument cases.

Good luck!

David

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David Salamon                Physics Graduate Student (Slave)
d-salamon@uiuc.edu           University of Illinois
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