Hi,
Short supplement to my presentation last AdHoc:
The reason why I did this presentation was to clarify the simplicity of the requirements coming from the objective “Do not preclude working within an intrinsic safe device and system”. Unfortunately the last slide with the “realization example” and the
following discussion again generated the impression of a complicated requirement.
From my point of view, the whole realization example is out of scope of IEEE802.3. Maybe it would have been better to call it “application example”. As I see it, there are no complex requirements concerning the whole “intrinsic Safety Issue”. Let me recapitulate
the four basic points from my slide:
- “Optional capacitive signal coupling with capacitance < 200nF / Line”:
- As an optional realization instead of the use of magnetics
- Capacitors can and should be seen as the usually used magnetics, as “non-existing” for the MDI
- 200 nF @ 1MHz < 1Ohm -> should not make a problem for the communication, but must be kept in mind
- “Optional Signal Amplitude Reduction down to +/- 0,5V”:
- Only required with a cable length <= 200m, so no additional constraint
- Full length is specified @ full signal amplitude
- Only meant as an application-specific option, adjustable via a Phy-Register
- “Optional external Termination Resistors of 100 Ohms (=50Ohms /Line):
- 100Ohms is the termination value anyway, so it’s just a realization option for the Phy IC
- “Optional Capacitive Coupling of the cable shield on one or two ends of the cable (<5nF)
- I don’t see any relevance for the communication and the MDI
I see the whole “Intrinsic safety”-Issue only as an APPLICATION for the 10SPE. It’s just that the outcome of our IEEE-Project should NOT PRECLUDE working with these very few requirements mentioned above. So, summarizing, keeping these 4 points in mind
while defining the communication is sufficient for that baseline proposal – from my point of view.
Mit freundlichen Grüßen
Jens Gottron
Siemens AG
Process Industries and Drives Division
Technology and Innovations
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