How to use a multimeter 4 - Current measurements

Here I'll explain in simple terms how to safely measure current. It's the hardest measurement to do.

Your SAFETY:

Connect DMM current leads with circuit DE-energised. Then turn on circuit to measure current (both current leads could be at supply voltage).

After use, don’t leave DMM set up for current. It’s too easy and dangerous to accidently use it as a voltmeter then  BANG!!

Unit of current is Ampere, symbol A; subunit mA;1000mA= 1.00A.

USE:

• DC current requires correct polarity of connections. Ensure the black lead is in the COM terminal. AC doesn’t care.
• The DMM leads must be reconfigured to current terminals (see photo), select appropriate DC or AC current range. The DMM is connected in series into the circuit as shown.
• Select a current range higher than expected. If unsure, start with 20A terminals and range and work down. (You will have to reconfigure leads/ range to measure mA - do this with circuit de-energised!) Overload is shown as 1   or OL .... switch off quickly otherwise you could blow the internal fuse or internal shunt in DMM.
• Here are examples of measuring AC and DC currents.

 

 

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