My table saw is nothing special, it is a Grizzly on the lower end of the price range.  I guess it is what is referred to as a "contractor" saw.  As with most other table saws, there is an adjustment for blade height and bevel angle - both of these adjustments are worm gear variety.  We can take advantage of that in setting the bevel angle by determining the angle that the blade is tilted per revolution of the adjusting wheel.  Before you do that, make sure that the starting position has the blade square to the table by checking it with a machinists square or a good drafting triangle.  Use a thicker blade that is less likely to have any warping.  Adjust the angle if necessary to make the blade square to the table and then make a note of the position of the hand-wheel.  Stick a piece of masking tape to the wheel marking the bottom or top - whichever you prefer.

Count the number of revolutions required to tilt the blade all the way over to 45°.  The hand-wheel on my saw made 30 turns to move the blade 45° - so that equals to 1.5° per turn.  Be aware that the worm gear might have some back-lash when the wheel is turned in the opposite direction.  Always set your angle by starting with the blade square to the table.  Now all that you have to do is divide the angle you want by the angle per turn to figure the number of turns of the hand-wheel to set your angle.  For example if you wanted to set the bevel to 30°, then 30/1.5=20 turns of the wheel.  The position marked with the tape should end up in the same location if the number of turns works out to a whole number.  If the number of turns has a decimal then you can just estimate where it should be and get reasonable accuracy.  This method is more reliable than relying on the angle scale.