Separation of Network Port from other Circuits including Patient Circuit

[Roland chung]

Hello Coves,

We have a medical device employs network port which is intended to be used for communication.

According to IEC 60950, the network circuit in the equipment is called TNV circuit. And the working voltage for TNV-2 or -3 circuit is 120 Vdc.

So, the barrier between TNV circuit and SELV circuits (e.g. RS232, USB port) should be 2 MOOP @120 Vdc, and patient circuit should be 2 MOPP @120Vdc.

Is it too stringent for the separations?

Thanks,
Roland

[Stijloor]

A Quick Bump!

Can someone help Roland?

Thank you very much!!

[Peter Selvey]

Handling of TNV is missing point in IEC 60601-1.

For MOOP it seems best to just apply the TNV requirements and limits from IEC 60950-1, as it is a special area and needs to consider things like surges (transients), ringing and so on not covered by simply using the nominal working voltage.

For MOPP, if the equipment is Type BF or CF, it seems reasonable to assume the additional F-Type barrier (typically 1.5kV/4mm) together with the TNV isolation is sufficient to provide 2 MOPP in total between the TNV circuit and the patient.

If the equipment is Type B, it might be best to consider on a case by case basis, depending on the type of contact the patient has with the equipment (e.g. transient, constant, plastic, metal, wet, dry etc).