NetBurner Community Forum

we've got some customer sites where we have rather high EMI bombarding
us, e.g., FM transmit tower. This was causing some problems there with our
ADC circuits - high impedence circuits problem?

anyhow, we're now back in the cert lab and around 10V/m2 we get the NB resetting.
we haven't gotten any further with the root cause analysis but since the NB is
someplace that they can readily see the affect, it falls onto my plate.

any ideas? any cert testing on the NB modules so i can point them elsewhere in our
design/product?

I'm not sure I completely understand. In the first part of your message it sounds like the external noise may be resetting the processor, but in the last part you are asking about a cert for the processor? We're probably in different markets, I'm only used to certs for the processor radiating noise, not the other way around. Is there a metal shield around the electronics you are trying to shield from the external radiation (coming in)?

what i am asking about has there been any testing as to how tolerant the modules are to
external EMI. NB has been helpful in providing some help on reducing the module's EMI.
we had our EMI generation tested, and actually externally generated, but now we're
getting rates bombarding us higher than we had previously tested. so i'm trying to find
out any suceptability levels that have been found, we're not after EMP protection here.

yes, we're in a metal case but we aren't isolated from it is as the external case provides
our radiant temp cooling.

Can you monitor the serial port and tell if its trapping or reseting?

I'm going to assume its resetting.

I've had EXACTLY the same problem with a wall wart power supply.
Specifically if you are running your AC->DC power supply at some small fraction of its
rated load they seem to be susceptible to external EMI.
The powersupply CE tests to get certified are only done at full load.

So first thing I'd do if you have a reproducible situation is try to see if the power supply is stable.
I've personally run a 5282 mated to a 900Mhz 1W transmitter with less then 2cm separating the 5282 and the TX antenna.

If it is a trap not a reset I'd have a different set of diagnostics.

Paul

FWIW, I have also used a mod5282 that is 5-6" from a VHF and UHF 5W antenna with no issues.

i was told that the unit "resets" directly to our application.
i haven't been there but i know no serial line was connected.
actually for the lab testing for this issue i believe all cables are
removed except for power. i don't think they are using the PoE
when this happens - let me check that.

i hope it isn't the power supply because we paid enough for it!
custom, don't ya know. our power supply is fed with a -48V line
and has 9 different output voltages, yada, yada.
though...