1.51 describe experiments to distinguish between electrolytes and non-electrolytes

When you place a conductivity probe in an electrolyte, current will flow through the circuit - this means you can measure its conductivity.

When you place conductivity probe in a non-electrolyte, no current will flow - this means you will get a reading of 0 conductivity

Another way to determine whether a substance is an electrolyte or non-electrolyte is to set up an electrolytic cell - if the substance will undergo electrolysis then it is an electrolyte, if not, it is not.