Help with using a multimeter
March 5th, 2017
I have this multimeter(check picture below) and I actually don’t know how to use it(got it as gift)
I have a few car and home chargers for different electronics and I’d like to find what’s the OUTPUT(V and mA) as it doesn’t say on the label.
Can someone tell me where should I turn the dial on the multimeter or how exactly I measure the output ?!?
Thanks a lot.
http://img192.imagevenue.com/img.php?image=74741_DSCN0117_122_135lo.JPG
Turn the dial until the blue part is on 200V (2 clicks left).
Attach the lead to the black “com” socket to the negative of the output.
Attach the lead to the red socket to the positive of the output.
If the meter (is it digital or analogue (needle) ??) registers too low, barely moves, switch the dial one click left again, to 20V
This will change the range of the meter – most laptop chargers are 19V output.
…..
The mA, amperage, is for current in a circuit, not for measuring the output of a charger – any reading you got would not mean much without a proper load (something plugged in)
….
Bottom left of the dial is for measuring resistors – again, set a medium value and couple up a resitor to the two prod-terminals, adjust the dial until you get a rading on the display or the needle.
Top right is for measuring batteries, it’s self explanatory.
I can’t see what the top-top right is, perhaps capacitance.
Ok, I got it.
But how do I measure the amperage of a cellphone charger ?
To measure the current (Amps) use the dark blue section marked with A
is right:
Turn the dial to the highest setting on the bottom right (“highest”, so you don’t burn the meter out).
Be aware that it’s not really an accurate method of measurement – current draw is device dependant as well as supply dependant.
As a guide to differences between chargers, it will work OK.
EDIT – on second look, it only goes up to 200mA, most chargers will pump out 2 to 5 times more than that, so don’t bother – the meter isn’t beefy enough to measure high enough.
My laptop charger output is 19V at 4.7A – 200 times what that meter can measure!
In other words DON’T connect a multimeter set to amps or milliamps across a power supply or charger !
It can easily damage your meter or the supply..
To measure amps(current), the meter must be connected in SERIES with the supply…And yours probably does not read high enough anyway..
Except by connecting the power supply to various loads and seeing if the voltage holds up, there is no simple way of determining it’s current rating.
Forget about measuring current on those things, your better off with a clamp on ammeter. Its not that accurate at measuring those little currents but will give you a figure.
Well at least I’ll measure the voltage so I don’t use the chargers one something with smaller voltage.
Ok guys, I guess that’s it.
Thanks a lot for all the info.
/thread
I’d say setting it to 20 volts would do for 99.9% of chargers.
Also, Polarity wise, In most cases, The inner part of the DC output jack is the positive (red probe) while
the outer is the negative (black probe). In some DC jacks, The inner part is so thin that you cannot fit
the probe into it, For such cases, I usually use a metal paperclip and bend it (Insert it while the charger is NOT plugged into the wall) and make the contact with the probe later. And just some precautions:
1. Always set the dial to the correct position before measuring stuff!
Inserting it to whatever you wanna measure, And then moving the dial is highly unrecommended!
2. If the probes are already attached to something, Remove em first before you turn off the multimeter.
Also, You might find this tutorial handy:
http://learn.adafruit.com/multimeters/overview
Anyways, Good luck!
Edit: Your particular DMM doesn’t have clear markings on the voltage types, So just to clear it up:
The white line voltages on the right side (200/300) are for ACV (AC Voltage) which is used by by electrical wires
on wall outlets and junction boxes, The ones on the left white line (2/20/200/300) are for DCV (DC Voltage) which is what
most chargers use for their output. The 1.5V/9V on the grey line is for battery testing. Make sure you use the DCV range for testing chargers, Unless you wanna fry your multimeter or cause a short circuit!