Why the voltage regulating resistor burnd out?

I made a voltage regulator using LM317T (circuit diagram attached).

when I switched it on and tried to measure the output voltage, the voltage control variable resistor (R2, 4.7K) burns out. why?

Is it because I tried to measure the voltage without connecting the load!!

If this is the cause, is there any way to measure volt without connecting load device (obviously, not getting the variable resistor burn again. I already burned 2)

I want to measure value of R2 for different voltage.
Not: max output is 25 +/- (for my transformer)

hi,
Have you checked that the diode across the 100R is the correct way around, or not blown short circuit.??