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How to measure DC current using a Digital Multi-meter also known as a DMM or Volt Meter

 

The diagram below shows an example of how you would measure DC current using a digital multimeter also known as a DMM.  The first step is to review your owners manual safety section. This is VERY VERY important.  Do not measure voltage levels over 12 volts without understanding the risk of getting shocked!!!   

Next read specifications to determine what are the current and voltage limits for your digital multi meter DMM.   If you want to measure the current through the cables from a car battery to a car engine - you would need an amp meter that can source over 250 Amps which is hard to find.  It would blow the fuse in a 10 Amp DMM very quickly!  If you have no idea if the current you are going to measure is over your DMM DC Current Limit or not, then try one of the following:

  • Look at ratings of what is supplying your voltage.  If it is a battery, look at the ratings on the battery.

  • If you know the approximate voltage limit of what is providing the voltage and the approximate resistance of what you are trying to drive with the voltage you can divide Voltage by the Resistance which will give you an approximate Amperage of your circuit. 

  ohm's law voltage resistance current DC  amps = voltage / resistance

  • Or try the approach of using precision current sense resistor by clicking here.   Or use a hall effect  current sensor shown here

 

Next hook it up as shown in the diagram below.

NOTE:  Many DMMs / Volt Meters use a precision current sense resistor inside to measure current. If you want to know how this works click here

 

NOTE- Do not exceed the current rating of your meter Ė it will blow a fuse.  Most meters can handle 10 Amps.   There is a way to get around the 10 Amp Limit.   To do this you would have to use two or three volt meters together and add the reading of all three together to get a total amperage reading.  If you want to learn more on how to do this, then send an email to brad@pedalpowergenerator.com

  

  1. Set  your meter to "AMPs" or "DC Current"
  2. Move your probes to the correct holes on the meter.  This is the most common mistake people make because they don't realize that the red and black wire probes must be plugged into the correct holes on the DMM to measure current.   (People donít realize that the test probes need to be different for measuring amps than they are for measuring Ohms and Voltage).   If you are measuring more than 1 or 2 amps on your meter, you would want to switch your DMM probe tips to use something like an alligator clips (Click on the thumbnail to see a big picture) 

  3. If you end up blowing a fuse it is a pain because then you have to drive down to radio shack or Fry's electronics to buy a new one.

   

 

 

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