a signal acquisition instrument , such as an oscilloscope , having an input stage that is referenced to a user &# 39 ; s ground is disclosed . information gathered by the input stage is stored in a storage element powered by a floating power supply that is referenced to the user &# 39 ; s ground . after storage , the storage element is disconnected from the floating power and from the user &# 39 ; s ground and switched to a power supply referenced to the remainder of the system . fet switching is beneficial , and information can be stored either in an analog format or in a digital format .