You can refer to CEMA handbook- Chapter 6. You may use the basic conveyor case for simplification. 

The manufacturer should provide the tension number.  To measure the tension you can use the belt length, the mass per meter, and the resonant frequency to solve for the tension.  The resonant frequency can be measure with an accelerometer, an adjustable strobe, or a laser operated sensor.  T = 0.0104 * K * L^2 * F^2  with T = static tension (lbs.), K = weight per inch (lbs./in), L = length of the free belt span (in), and F = natural frequency of the belt (Hz) as can be found on websites.

You can refer to this note.

you can refer to text book on machine design by J. Gputa 

So Asyraf please look for the materials.and read it. Remember Tell me I know, Show  Me I will understand , but if I do it myself I will remember

Use any one type of spring or bolt / nut