This is normally an indication that Earth and Neutral are connected together in the installation. Readings should be greater than 1MΩ for an Earthed system, or 2MΩ for Class 2 or “floating” systems. Ideally this reading should be as high as possible. PV150 can read up to 19.99MΩ, and the PV200/210 up to 199.99MΩ. A good result would be “>19.99MΩ” on the PV150, and “>199.99MΩ” on the PV200/210.