题目内容
步进电机可以直接由直流电源来驱动。
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Analog multimeters have a LED display and the digital has a needle.
All digital meters contain a electrical motor to power the display so they use virtually no power from the circuit under test.
This means that on their DC voltage ranges they have a very high resistance of 10 MW or more, usually 100 MW, and they are very unlikely to affect the circuit under test.
An analogue meter can be safely connected in reverse, but the digital meters may be damaged.
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