Electronics > Beginners
Hooking up 4 x 3v LED string lights to a 6v PSU
Brumby:
--- Quote from: Brumby on February 03, 2020, 02:15:45 am ---Yes, this means you have to break the circuit to do a current measurement ...
--- End quote ---
This is when you use a typical multimeter. There are other options using a clamp mechanism.
Using the clamp style, AC current measurement is easy, which is why you see these everywhere. DC requires a different approach which is a bit more involved.
The most commonly cited meter is the UNI-T UT210E. This is a clamp-style meter which has DC current measurement - and it is not expensive!
All you have to do is place the clamp over ONE conductor and it will measure the DC current. Resolution is 1mA, but accuracy is less as you need to deal with the fluctuations in the reading due to other magnetic fields. This meter would still be quite OK for the sort of measurements you are doing.
bob21:
Yes, that’s how I tested. So the Uni-T looks like a must have for the toolbox.
Ok, so how does this sound for a plan:
1. Order the Uni-T
2. Use to test the draw of the entire circuit
3. Reattach each AA cell pack to its respective string and test the current draw of each so we know what they each draw (if this is possible)
Would this provide helpful information?
I’ve only ever used a non-clamp cheapo meter just to test cells and continuity etc. so I welcome something better for the toolbox.
Brumby:
The clamp goes around ONE wire. The meter does not have to touch any wires at all. All clamp meters work on the magnetic field generated by flowing current.
Don't put both wires coming from the supply through the middle. If you do, the magnetic field from one wire will be cancelled out by the other.
bob21:
Just edited my post because I noticed you said attach to one wire, but I did actually think it would have to make contact. This sounds awesome! Amazon have them and my friend has prime. Watch this space ;-)
Brumby:
Here's one example of wrong and right...
The same rule applies for DC as it does for AC.
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