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I notice that the +/-1.2V range is floating. ( ref. https://moosh.im/wp-content/uploads/2015/01/MooshimeterCheatSheet-V0.pdf )
What exactly does this mean? I.e – in respect to what is the input floating?
In my understanding, it is meant as an exception of the otherwise general “10 MΩ input impedance”.
“Floating” means the input is “left to itself”; there is at most a capacitive, but not a defined conductive path to ground, so the input resistance for DC can be considered as “∞”. Think of it as an open CMOS input which is completely isolated by an oxide layer, so it has no defined potential in respect to ground – it is “floating”.
See also this thread.
Thanks! All clear now. :)
Just by the way, is it correct to describe an input of a measuring instrument as “floating”? It’s absolutely not a problem for me – I’m just asking out of interest. The input must have *some* impedance, being partially resistive and partially reactive. It may be very high, but it’s not infinite. If the exact characteristics aren’t known, would it then be more accurate to specify some safe minimum (e.g 100M ohm or whatever), and say “> 100Mohms”, plus if the capacitance is known, specify that as well etc etc.
Again – it’s not a problem for me – just asking out of interest to further my understanding.