The non-uniform dc glow discharge plasma system is studied by using isolated computer controlled three couples of double probe system (TCDP)in argon gas, simultaneously. The double probe is more applicable than the single probe in diagnostics, specially in plasma reactors which have insulating or semi-insulating walls. TCDP technique has been developed to use for magnetized, un-magnetized, and for low oscillating plasma systems by using optically isolated circuitry to minimize the measurement errors with higher resolution and accuracy. Changing the shapes and diameters of the tube from region to region leads to change the in plasma properties. As the diameter of the tube is decreased at constant discharge currents, the density increases and the electron temperatures decreases.