Single ended - Floating

Single Ended Floating signals which are not electrically connected to ground. The signal appears between the two terminals of the signal source. This signal can either be a voltage source or a current source.

An ideal voltage source has a near zero internal impedance - a battery for example. A pH electrode is a voltage source but this has a very high internal resistance. An accurate reading can only be obtianed with a measuring circuit whose own internal resistance is much higher than the source resistance of the source. Voltmeters therefore need to have a high internal reistance - ideally infinite.

An ideal current Source has a near infinite internal impedance - a solar cell. In this case to measure the source current the measurment impedance should be very low. Ammeters therefore need to have a low internal resistance - ideally zero.

Here is a picture: