Neither, AC/DC means AC/DC, it means the specification of the power supply is AC input DC output.
AC=Alternating Current, DC=Direct Current, AC/DC that is, will be converted to DC, the power flow can be bidirectional, the power flow from the power supply to the load is called "rectifier", the power flow from the load to return to the power supply called The power flow from the power supply to the load is called "rectification", and the power flow from the load back to the power supply is called "active inverter".
AC/DC converter input for 50/60Hz AC power, because it must be rectified, filtered, so the relatively large size of the filter capacitor is essential, and at the same time, because of the encounter of safety standards (such as UL, CCEE, etc.) and EMC directive restrictions (such as IEC, FCC, CSA), the AC input side must be added to the EMC filtering and the use of components to meet the safety standards, which limits the AC/DC converter input to 50/60Hz. This limits the miniaturization of the AC/DC power supply size.
ExpandedDigital multimeter can not only measure DC voltage (DCV), AC voltage (ACV), DC current (DCA), AC current (ACA), resistance (Ω), diode forward voltage drop (VF), the transistor emitter current amplification factor (hrg);
Also can measure the capacitance (C), conductivity (ns), temperature (T), frequency (f), and added for the AC/DC power supply to be smaller. (f), and increased to check the line through the buzzer file (BZ), low-power method of measuring resistance file (L0Ω). Some instruments also have inductive file, signal file, AC/DC automatic conversion function, capacitance file automatic conversion range function.
Most digital multimeters have added the following new and practical test functions: readings hold (HOLD), logic test (LOGIC), true RMS (TRMS), relative value measurements (RELΔ), automatic shutdown (AUTO OFF POWER) and so on.
Baidu Encyclopedia--AC/DC