That depends on the sensor application. Some sensors are not chloride tolerant and need low chloride electrolyte. Most sensor electrolytes are buffers, so it really depends on the application of the sensor.
As Shelley points out, most electrolytes used in sensor applications will be biological buffers. I attach a very useful resource that I hope you will find useful.
'Buffers: A guide for the preparation and use of buffers in biological systems.' [CALBIOCHEM]
Thank you all. Actually i am also using buffer solution for my sensor application (Pharmaceutical compounds). Can i use this (NaCl + KCl) for electrochemical reduction process like Ag, Ni nano particles deposition purpose.
As Shelley and Parahuram point out, it's difficult to provide a suitable answer without knowing more about the specific application. What types of compounds are you looking to detect? Interference of the chloride ion would be my biggest concern. What potentials are you looking to use?
Did you look at the booklet I sent? It has some good general guidelines and examples to look at.