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Sensor Electrical output question

So I'm building an interface to an Edwards Active vacuum Gauge tube (aka a fancy sensor).

I'm reading the manual (go figure :).. and stumble upon this lovely little bit:

"Do not connect the electrical supply common (pin 2) to the signal common (pin 5). If you do, the AIM Gauge pressure output signal will be inaccurate."

Oh.. well, ok.. The question is, are they trying to tell me the output of the sensor (which is 2 - 10vdc depending on pressure) is actually a differential output?

IF it helps, here's the specs on the output signal (again from the manual)

Range 2

Reply to
James Lerch
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They have a drop in the ground wire due to the current in it. It is a fairl;y common problem with fancy sensors that have long wires.

Going differential is the way to solve the problem. It only adds a little cost. You could also float the power and ground the signal return but that adds more cost.

Reply to
MooseFET

It looks more like they provided a 4-wire active Kelvin connection and they don't want him to screw it up by sharing signal common with power ground. Sometimes the questions are just so odd it's difficult to fathom the lack of sense.

Reply to
Fred Bloggs

Hmm.. so, do you think it would be ok to tie the commons together back at the display unit / power supply? IF it was really a differential output, they would probably mention that, right?

I guess a little op-amp wouldn't be the end of the world :)

My plan was to use the $20 AVR-Butterfly as the display unit, I'll need to go re-read the atmega169 docs and see if it has an analog differential input..... Hmm maybe.

Thanks for your time (again!)..

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James Lerch
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Reply to
James Lerch

Oh, Fred, You're just so brilliant! Swoon ;-)

...Jim Thompson

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|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
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Reply to
Jim Thompson

James Lerch snipped-for-privacy@tampabay.no-spam-seeds.rr.com posted to sci.electronics.design:

No, don't do that.

The signal common is a derived reference, trying to connect it to other references or grounds defeats its purpose.

I like the perseverance sig.

Reply to
JosephKK

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