Earth monitoring of individual plant sections is common, as interconnected process items must be kept at the same electrical potential and bonded to an earth connection.  Unearthed transfer pipes and ducting are prone to static build up and are often earth monitored, particularly when they are disassembled regularly for cleaning etc.

It is very important to ensure that the monitoring equipment selected will not allow the sum of circulating currents from the various channels to exceed permitted levels for Intrinsic Safety.

NFPA 77 states that: Resistance in continuous paths will typically be less than 10 Ohms.  Greater resistance usually indicates the metal path is not continuous, usually because of loose connections or corrosion. (6.4.1.3).

>| Applications Home Page