A multi-meter is an electricians device for carrying out a wide variety of electrical tests on various different systems. These tests can include verifying the Ohm rating on your heating system and checking that the system does not have a fault to earth.

It is imperative that only competent individuals should carry out any electrical tests and, if in doubt, you should ensure that a suitably qualified electrician is contracted to carry out the work. All new electrical installations in the UK must be Part P tested by a qualified electrician.