Measuring voltage on ac adapter
Since you're not getting any reading for two different adapters there's indeed a chance that you're doing the measurement wrong.  

Is the AC adapter also AC out? If it is, then you'll have a zero reading if your multimeter is set to DC. Setting the multimeter to read AC voltages you should get a reading different from zero, even without a load. The voltage will be higher than the rated voltage, like a 12 V AC adapter may give 14 or 15 V without load. Likewise, if the adapter has an unregulated DC output the unloaded voltage will be higher than the rated voltage.  

So, check that you're measuring AC voltages with the multimeter in an AC position.