The housing is of metal.
Furthermore, all in- and outputs is protected with filters.
The filters increase the reliability and availability of the ammeter and are not a part of the safety measures. This means that failures in the EMC protection have no consequence for the safety functions.
If the ammeter is measuring the current in a lamp or a point or another object at the station and this is done through long cables then these cables can pick up energy rich pulses and noises (e.g. by lightning or when the pantograph is activated).
In such a situation, all internal components can fail arbitrarily at the same time (multiple types of failures occur). The safety principle can handle this situation.
The internal microprocessors and communication circuit are galvanic isolated in order to increase the independence between the elements.
This galvanic isolation is solely a filter, implemented to increase the reliability. It has no safety functionality.
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