How to ensure the instrument is shock free?

Hi all,

Actually I have an instrument to detect component failure.
Which is operated at 230V AC @50HZ. If instrument properly connected earth..when I test earth to neutral voltage it's around 3V AC..
If i removed earth from the instrument then i measured the voltage between Neutral to the Instrument Body it shows around 105 Volt, Is it right way to test the instrument?
How can i ensure the instrument is safety and shock free?
Please share us your suggestions because if suppose earth got failed no one get affect due to this 105 Voltage

Awaiting for your positive feedback..