Ingress Protection Rating – in brief
IP (or “Ingress Protection”) ratings are defined in international standard EN 60529 (British BS EN 60529:1992, European IEC 60509:1989). They are used to define levels of sealing effectiveness of electrical enclosures against intrusion from foreign bodies (tools, dirt etc) and moisture.
Each protection rating (IPsl) can tell you about the solid particle protection – s, and the liquid particle protection, l.
For example if the meter you require states it has an IP54 rating then it is “Dust Tight” – s=5 and protection against splashing water – l=4.
If you are wishing to mount your display outdoors then you will require at least IP65.