I have a device (an ADSL modem) that when plugged in to an ac adapter does not seem to do anything (power light stays off).
I would like to know how to measure voltage for an ac adapter to make sure it is working. I have multimeter, but when I connect the inner and outer rings of the supply, it does not register any voltage (I assume it probably needs some load in order to give a voltage but I am not sure).
Output rating is 12 V / 1.4 A.
I tried with a different ac adapter and it also did not register voltage. Yet while measuring a AA battery it shows correct values, which leads me to believe that I am not doing something right.