What is maximum range of voltage measurement?
It's an interesting question and I've often wondered if any other technology works over such a wide range. 


  I would hazard to guess that there is some physical limit to the range of voltages that can be practically measured in an electrical circuit.


Except maybe for extreme natural phenomena, the upper voltage limit will be for measurement of man-made voltages. The electrical power distribution industry uses voltages of up to a million volts for long-distance DC transmission systems. Since they monitor the line voltage readings at 1 MV are routinely done. The labs testing the insulation for such systems will have to generate voltages far in excess and will measure the voltages generated.



Figure 1. For ultra-high voltage measurements your multi-meter probes aren't going to be enough. Source: HF-Instruments.



For low voltage measurements the subject is more tricky due to noise. Kiethley's Low Level Handbook is an excellent read on the subject.



Figure 2. Voltage measurement and instrument types. White is possible, grey is tricky and black is impossible.


  The theoretical limit of sensitivity in any measurement is determined by
  the noise generated by the resistances present in the circuit. As discussed
  in Sections 2.6.5 and 3.2.6, voltage noise is proportional to the square root
  of the resistance, bandwidth, and absolute temperature.
  Figure 1-2 shows theoretical voltage measurement limits at room temperature (300K) with a response time of 0.1 second to ten seconds. Note that high source resistance limits the theoretical sensitivity of the voltage measurement. Although
  it’s certainly possible to measure a 1μV signal that has a 1
  Ω
  source resistance, it’s not possible to measure that same 1μV signal level from a 1TΩ
  source. Even with a much lower 1MΩ
  source resistance, a 1μV measurement is near theoretical limits, so it would be very difficult to make using
  an ordinary DMM.