Simple guide to using a DMM for measurements

[HKJ]

I have added a few more measurements and some notes to the guide.

 

[Mr Happy]

Looking at the comparative readings with the Fluke meter, that BEST meter seems to be quite accurate. Many will wonder if that degree of accuracy from cheaper meters is typical, or if it is a "fluke"?

 

[HKJ]

Looking at the comparative readings with the Fluke meter, that BEST meter seems to be quite accurate. Many will wonder if that degree of accuracy from cheaper meters is typical, or if it is a "fluke"?

I do not have much experience with cheap meters, but as far as I know they usual are quite accurate, except when they are not (Like when the battery is low or measuring on a "strange" waveform).
The cheap meters are also much more exposed to damage from misuse. the Fluke meter can basically not be damaged from any ordinary voltages, the worst you can do is blowing a fuse in it.

 

[LuxLuthor]

HKJ, it is obvious that you spent a lot of time putting this together with excellent photos, and logical discussions. Keeping it simple is not always easy, but you did it very well.

Thank you for making such a wonderful contribution to the community. :thumbsup:

 

[VidPro]

yup excelent guide and great clear clean pics.

With such great guide/pics, could you do the Bench power supply too
(or not, just asking)

 

[HKJ]

With such great guide/pics, could you do the Bench power supply too
(or not, just asking)

I do not really know what kind of guide to make for a bench power supply?

If it is how to connect it to a flashlight for measurement it can be a bit problematic, due to the current draw from some lights (See the oscilloscope curve in my first post), not all power supplies works well with this kind of current draw.

 

[VidPro]

I do not really know what kind of guide to make for a bench power supply?

If it is how to connect it to a flashlight for measurement it can be a bit problematic, due to the current draw from some lights (See the oscilloscope curve in my first post), not all power supplies works well with this kind of current draw.

i havent had any problem hooking up flashlight heads to voltage current controlled type bench supplies. probably the readings on my cheap stuff are just averaging, but that is all i need to know.

How the flashlight head (bulb or led or whatever) reacts to different voltages, for the purpose of determining the battery it can handle, if its buck or boost, the regulation, and how long it will last with that battery type, overdrive and all that stuff.
then how to charge various batteries using voltage-current controls.

one could start with the most simple thing, lighting up a LED, and finding out things like VF, smoking a led to test durability, taking a incan bulb over spec to see where it pops at.

powering charge curcuits , drivers, gadgets, to see thier current draw.

just about anything you did with the Meter, you can do stuff with the bench supply., and lots of that could be done with a <1A supply.

 

[HKJ]

i havent had any problem hooking up flashlight heads to voltage current controlled type bench supplies. probably the readings on my cheap stuff are just averaging, but that is all i need to know.

How the flashlight head (bulb or led or whatever) reacts to different voltages, for the purpose of determining the battery it can handle, if its buck or boost, the regulation, and how long it will last with that battery type, overdrive and all that stuff.
then how to charge various batteries using voltage-current controls.

one could start with the most simple thing, lighting up a LED, and finding out things like VF, smoking a led to test durability, taking a incan bulb over spec to see where it pops at.

powering charge curcuits , drivers, gadgets, to see thier current draw.

just about anything you did with the Meter, you can do stuff with the bench supply., and lots of that could be done with a <1A supply.

I got you idea and it could be interesting to do that kind of guide, but it will have to include not only "how to", but also something about what to do with the measurements. I.e. if a led is measured to have a Vf of 3.2 volt, what practical implication does that have (One is that a boost regulator and LiIon would be a bad idea).

I am using a 0-15V 3A supply for testing flashlights, where I have replaced the voltage potmeter with a 10 turn potmeter. That is a big improvement and I might also do it on some of my other power supplies.

I do not have time to do it in the next couple of weeks, but maybe later.

 

[VidPro]

yes it would be more "text" based , but with pictures
pictures in a post tell SOOO much, and make things look a lot simpler, like what you have here qualifies as "Worth a Thousand Words":thumbsup:

 

[hazna]

thanks for the guide, I'm a complete newbie to DMM...

Could you also explain how to measure the charging rate from a charger with the DMM? Thanks

 

[HKJ]

Could you also explain how to measure the charging rate from a charger with the DMM? Thanks

Ok, it is added to the guide.

 

[hazna]

thanks for the update, HKJ! :twothumbs

Got a question though, in regards to measuring the output from a charger... why do you put both the metal foil pieces on the positive end? (thought you would put one on the positive and one on the negative) As mentioned previously, I'm a newbie when it comes to this sort of stuff.

 

[HKJ]

thanks for the update, HKJ! :twothumbs

Got a question though, in regards to measuring the output from a charger... why do you put both the metal foil pieces on the positive end? (thought you would put one on the positive and one on the negative) As mentioned previously, I'm a newbie when it comes to this sort of stuff.

When measuring current I need the meter in series with the battery, like this:

Charger----meter----battery------charger

If I had wanted to measure the voltage, I would have to connected the meter to both ends of the battery and use the V/OHM terminal on the meter.

 

[kosPap]

Re: Simple guide to measuring on a flashlight

I prefer to measure the voltage drop across a one-tenth ohm 1 % 3 or 5 watt resistor and use ohm's law for current measurements. Most VOMs read DC voltage better than current.
...snip snip...
Curt

HKJ I am glad you made this guide...sadly i found it after I discovered how to make these measurements by other sources...and by shear luck I made my first current mesurement on a resistor thsi morning!!!

But for the benefit of the Newbees could you add a section on current mesurement with this method? (both pics and calculations)

thumbs up my friend, kostas

 

[HKJ]

Re: Simple guide to measuring on a flashlight

HKJ I am glad you made this guide...sadly i found it after I discovered how to make these measurements by other sources...and by shear luck I made my first current mesurement on a resistor thsi morning!!!

But for the benefit of the Newbees could you add a section on current mesurement with this method? (both pics and calculations)

thumbs up my friend, kostas

It is more complicated to use a resistor and the result might not be any better, it might be worse, but that depends on a lot of factors.

But if it is wanted, I can add it.

 

[karlthev]

I just saw this...great thread and job on this!! Thanks.


Karl

 

[nfetterly]

Wow - thank you for the superb effort here. Wonderfully illustrated! I know that I can make use of this - I've only been using my (cheap) meter for very basic stuff, not as much troubleshooting as I will be able to now.

Neale

 

[mbiraman]

Great job HKJ. I was wondering . On the ZTS battery tester under 3.6v you see listed a number of batteries but not 14500. My aw 14500's are 3.7. Does it matter ?? . Can the 14500's be tested in the 3.6 spot??

 

[HKJ]

Great job HKJ. I was wondering . On the ZTS battery tester under 3.6v you see listed a number of batteries but not 14500. My aw 14500's are 3.7. Does it matter ?? . Can the 14500's be tested in the 3.6 spot??

Yes, it can, it is about the same as RCR123A/16340.

 

[mbiraman]

Yes, it can, it is about the same as RCR123A/16340.

Thanks HKJ