Hi Paolo
now we get the truth. It a phenomenon We observe very often:
In your case following happens:
You apply the pulses on common mode to the whole system (printer),
especially to the housing (if any) or to metal parts.
Currents flow back to the EFT generator through the interface lines, in your
case through the network cable.
Thus the worse case should be:
-apply the EFT pulses to ALL THREE lines
-connect the other end of the (shielded) network cable to the
ground reference plane.
Thus you will have the highest currents through this line.
Since the coupling capacity in the EFT generator is about 33nF, you will
possibly
observe more severe disturbances then when coupling the pulses into the
network cable using the capacitive coupling clamp (about 200pF).
You did not tell us what kind of network you use.
A: Thin wire (coax, 50Ohm)
If you use thin wire ethernet the shield of the RG58 cable is not connected
to the chassis. If the BNC connector is not capacitively decoupled (e.g.
10nF, very short leads, between cable shield and chassis) it is not worth
testing. I did not see any computer or peripheral of this kind that meets
the requirements.
B: UTP (unshielded twisted pair)
Your EUT might have a chance, depending on the layout of the network PCB
C: STP (shielded twisted pair)
The only solution that really works. Check the RJ45 connector (should have
connections for the shield and should be contacted to the housing of the
EUT).
Good luck
George
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* Dr. Georg M. Dancau * HAUNI MASCHINENBAU AG *
* [email protected] * Manager Technology Research *
* TEL: +49 40 7250 2102 * K.A.Koerber Chaussee 8..32 *
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----- Original Message -----
From: "Paolo Roncone" <[email protected]>
To: <[email protected]>
Sent: Thursday, June 08, 2000 2:08 PM
Subject: Re: EFT/Burst
>
> Thank you for your replies to my first inquiry.
> In particular, George's observation that sec. 7.3.1 applies only to
post-installation tests made me realize that I missed the right point in the
standard, that is sec.7.2.2. I just don't understand why the guys who wrote
the document were not specific in the more important (and used) case of
tests performed in labs (those are mostly the ones used to verify
compliance). So they leave the door open to any possible combination of
phase/neutral/ground when applying the bursts to the AC line.
> One important point that I didn't mention in my previous note was that the
failure is not specifically related to the printer, but to a LAN/Ethernet
box that is attached. Our OEM got 2 different printers to fail under the
same conditions (bursts with positive polarity @ 1kV applied to Line and
Protective Earth (PE) simultaneously) with the very same box attached. The
printer stops printing and go to a Ready state. You are able to make the
printer Not Ready and back to Ready, but it does not continue to print. the
PC driving the printer says the data timed out sending to the device.
> The same printers don't fail when tested without this LAN box.
> Our feeling is they want to pull us into working on the problem because
the vendor of the LAN box is not so willing or able to help.....
>
> Of course any additional hints can be very helpful.
>
>
> Paolo Roncone
>
>
>
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