@Van Wang Appreciate Video clip! Sorry for butting in, I would love your initial thoughts. Have you tried - Franaar Shining Shape Formula (just google it)? It is a great one of a kind guide for revealing the secret to repair your electronic devices minus the headache. Ive heard some amazing things about it and my m8 finally got amazing success with it.
Thank you for posting. This is the best and simplest explanation I've ever seen. If you ever expand it, please add the same test for the amperage output of a solar panel.
Thanks very much for this. Outstanding demonstration. Makes sense. You have to break the circuit to see the flow of current. I was very lucky I didn't break the meter before I saw this. Thanks very much.
Doesn't say why there is a resistor, or what size resistor, or what happens if there is no resistor. If I don't have a resistor and bulb, can I use a PC fan instead?
If he had done without the resistor, more current would then flow (higher reading would be measured on the multimeter). But he used the resistor to protect the bulb, so it's likely that without the resistor, the high current and full voltage across the bulb would have blown the bulb.
I have a cheap multimeter with 20A fuse that can do 15 sec. max C test. A couple of times i have tested batteries under 20A (without a circuit) and the cable got hot, so i always do 4 sec test. My meter is still okay, your advice is also good
Great job. I'm sorry he passed away. Wanted to ask why its okay to put the multimeter probes on directly on a battery to measure voltage, but not in the amperage setting? Anyone welcome to chime in.
just learned in school, measure current going through, voltage across. Essentially when measuring voltage it’s okay considering you’re just measuring a potential different between two terminals. Thus measuring the open circuit voltage whilst putting a positive on hot, negative on ground. When measuring current, putting an anmeter in parallel to a source, you’re shorting it, like connecting a wire, infinite current passes through the short and which drains your battery because V=IR.
More of them than us, world over that is.. And by far more in need of money.. So You-Tube pays per view, thus they flooded You-Tube with crap video's.. Most are not good or right, just in need of $7.23 per month from stupid-tube.. Sad..
So are you telling me, I have to buy a bulb, a bulb holder and a resistor to measure the amps on a battery?...and how the heck do I know what resistor to use for all the different types of batteries....😖
I am installing a video doorbell. It says my transformer has to be min of 16 vAC 10 VA, but how do I measure that? The meter only seems to measure DC amps. Why is that? Thanks.
How would u check currents (amperage) of a used Harbor Freight 25 watt Solar Panel with the same type of Ammeter .. is there a way to test the panel alone with no battery or load?
I've done this but it doesn't make a circuit and reads 0.00. Has the fuse blown previously with something I did long ago? I would have thought the mulitmeter just wouldn't work if that was the case By the way got the test correct at the end. EDIT: It is showing low battery on the multimeter... maybe that's why?
He's 100% Correct. If you go Directly to the Pos and Neg Post with the Multimeter? You'll blow The Multimeter... Why I'm Telling you this is? Because I FREAKING FORGOT!!! THAT'S WHY!!! LOLOLOL Which is why I came to this Video... I haven't tested Amps IN OVER 20 YEARS... They say If You Don't Stay working with Electronics? YOU'LL FORGET STUFF... I'm Proof "Positive" of that reminder. However, Luckily? I didn't blow The Multimeter. But The Wires caught hell... LOLOLOL!!! Great Video, and Thanks... I'll Be Bock...
So that's DC power, but for measure AC current in 110v or 220v house electricity, most have something connected on outlet running on, that's right ? eg: transformer, coffee maker or something like that, drawing power.
Okay, so you are using a "conventional view" of current flow. Actually in d-c circuits does not the flow come from the negative side of the battery? Should the set up and schematic show this?
Hi, i have a power supply 12v 20A connected to a step down convertor, i want to get a current of 5A using the convertor, like in your video where you used a lamp and resistor, what should i use so i can adjust the current from 20A to 5A? Thanks
Good job! But what I don't know now, is how to do this (measuring current) off of a solar panel. Could you tell me pls? I have searched and couldn't see your video on this. Thank you in advance.
First, a warning. Do not attempt this with a large solar array. Some of them put out many amps at several hundred volts. This type of system is extremely hazardous and not for amateurs. I will assume you are trying to measure a small panel, up to 12 V and a few amps. To do it with this type of meter you will have to disconnect the positive output wire that goes from the panel to the load. Configure the meter for the 10 A setting (assuming your panel puts out less than 10A), then connect the red (+) probe to the panel output, and the black (-) probe to the load wire you disconnected from the panel. The load must be connected to get a useful current reading. Be careful with this much current. A better type of meter for measuring high power circuits is a clamp-on meter, which clamps around a single wire and does not require breaking the circuit or touching any live wires. Make sure you get one that measure DC current if you want to work with solar panels.
The 22 ohm resistor is in the circuit for two reasons: 1) to limit the current to the bulb, 2) as part of the video series "Measuring Resistance with a Digital Multimeter".
Each circuit on a car is protected by a fuse. Each fuse is labeled with its maximum amperage. Almost every fuse in a car is at least 10 Amps, but the circuits generally draw much less current. The best use for the ammeter in a car is to find small "leaky" or "vampire" currents, meaning devices which are drawing current when you expect them to be off. A lot of electronics in modern cars (stereo, alarm systems, door locks) stay alive all the time and draw a small amount of current (10s of milliamps). So it can be useful to use the ammeter to find vampires if your battery is dying rapidly. For example, I had a car which drained the battery in a few days. It turned out that there was a small current drain in the power seat memory. One of the buttons was stuck "on" so it continued to draw current and kill the battery. Using the ammeter on a powered-on device like headlamps or stereo is very risky since they will likely draw more than 10 Amps and blow the multimeter's fuse. It is less risky to use a voltmeter at the device to see if it is receiving power. See my video "Measuring Voltage with a Digital Multimeter".
Hi , I'm trying to do an amperage test on my stanley Jumpit jumper starter pack . Jumpit Jump pack rated at 1000 peak battery amps and 500 instant starting power . ..... On my jump lead of my pack red & black clamp ....... would you walk me through the setting on my multimeter to read amperage out from my pack lead ? Greatly appreciated .... thanks
Great vid - thanks - looks like I have to replace my fuse now, lol. I usually only deal with voltage/resistance for diagnosing car electronics, but I inherited a battery charger and wanted to test if it worked. Multimeter only supports 10A current, battery charger had a 2A (12v DC) option I wanted to test. I hooked it up in parallel to the battery on the loaded circuit, it sparked (the probes arched) a little when I connected the probes, no good reading, then unloaded, tried again, same results, now no sparks, lmao. Hopefully can replace that fuse. Should have watched this video first!!! I'll replace the fuse and try it in series this time... For the 20A and 60A settings, I have to buy a new multimeter I guess. Any easier way to validate these? Seems most multimeters I find only go up to 10A on the current.. EDIT: As a side note, if I test the voltage on the loaded circuit it's ~12.85 (typical charging output on a 12v auto DC circuit), but if I don't load it (if I test both alligator clamps that you'd connect to the battery) I only get ~9v. Is this normal? I would have expected to see 12.85 with or without a load. Thoughts?
To measure currents greater than 10 Amps, you will probably need an inductive-clamp type meter. It has a sensor that clamps around one wire and uses magnetic field to measure current. The clamp units do not require you to break the circuit, but the clamp can be clumsy to use in tight spaces. Make sure the one you use has capability of measuring both DC as AC (some only measure AC).
What would happen if you connect the negative lead(-) coming from the the amp meter/multimeter to the negative terminal(-) of the light bulb instead of the resistor(+) connected that's connected to the positive(+) terminal of the bulb? Would the amp meter/ multimeter still measure amperage drawn?
All these UA-cam video show how to measure current on a simple circuit. Most of the time you will be trying to measure current in a wire so it becomes somewhat of a mess. For example, if you want to measure the current on a lamp, you would have to cut the wire just to get to one wire to get in series to measure it. If you're lucky your lamp will have one of the double wires where all you have to do is separate the two wires and put a clamp meter on it. If you don't have a clamp meter then you will have to cut one of the wires or both because you won't know which is the hot wire. These guys show you how to measure it but it is no where near a real world way to measure. Get's even more complicated when you are dealing with a big circuit where everything is grounded to a common wire.
No, the resistor is not necessary for this task, but it is part of the same circuit that is explained in my Measuring Resistance and Measuring Voltage videos.
so this will just measure the current being drawn for the circuit right? but what if we want to know the total current the power supply can put out? or is there no way to tell unless you know what the power supply is rated for already? i have an old power supply harvested from a PC and i use the the 5v out to power some led lanterns i have hanging on my porch but now i want to add a USB to it to power a security cam , i am just afraid it might be too much current though i read that current of the power supply should not excede double or 2 and half times what the load runs on , for exampe the camera comes with a 1A USB power brick and you can daisy chain up to 3 cameras off that one brick , but i will say 1A for the camera load , so if the PC power supply is rated at over 2.5A then will that be too much current and fry the camera?
Can you check the amps of a circuit when it's not under load? I have a 12v power distribution module for which each circuit can have the amperage set by a computer program. I lost the programming cable, so now I want to check how many amps each circuit is set to so I can be sure I wire a new accessory to a circuit with the appropriate amps set. Or does the circuit need to be under load, and would I need to increase the load until the breaker tripped?
Current must be measured on a live, loaded circuit (unlike voltage , which can be measured on a live but unloaded circuit). Electric current is just like water flowing in a pipe; only when it runs is there anything to measure. If you do test the breakers for maximum load, please make sure that you don't burn down your shop.
Hi MrChanPhysics. I just watched your video. it looks great for me without any electricity or electronics background. I followed your tutorial piece by piece, setting exactly as you did BUT my multimeter read (1.) I am using 3AA batteries to operated a 3-led diodes of a PIR sensor light and I need to know the current so that I replace the batteries with a mobile telephone charger using the USB. Am I doing something wrong pls?
If the meter reads "1. " it probably means it is set to a scale too low to display the current. Try starting with the 10 Amp setting.. This may require you to move the red test lead to a different socket as I have shown in the video.
hi Alls, may I know what value voltage and watt of the lamp that used in this video? I already tried and follow the step in this video with 24VDC 70W lamp and should be 2.9A by calculation right. but I only get 0.25mA. any idea?
in that case, the negative terminal of the battery connects to the negative of ammeter and the positive of ammeter is connected to the negative terminal of bulb... am i right?
Urgent question for daughter's 3rd grade science project! We measure batteries in series and parallel connection. 2 AAA 1.5V batteries in Series go to 3V and supposedly the 1000 MAh stay the same, 2 AAA 1.5V in parallel stay at 1.5V but the Mah doubles to 2000, and 2 x 2 series connected in parallel go to 3V and doubles to 2000 MAh. I can measure the voltage increase or stay at same with the multimeter, plus I use a light bulb showing dimmer or brighter light, but how can I demonstrate the mAH increase for this purpose? I thought your video did that, but I get a reading of 0.12 and in parallel nothing changed. Using D or 9v I get the same readings when I though it would definitely be higher then the AAA battery. Do I need something else to show this or can this only be measure over time? Just a simple proof of hypothesis to double the mAh in parallel would be needed. Thanks.
The current (mA) will not change between 1 battery or 2 batteries in parallel (as long as the batteries are fresh and the bulb is a low-power flashlight type). The bulb is a type of resistor (R). The "formula" for current (I) is I=V/R. This is known as Ohm's Law. Since AAA, AA, C, D batteries all have the same voltage Vbatt, they will all supply the same amount of current I through a resistor or bulb R. If you put two batteries in series, then you have doubled the voltage Vbatt and according to Ohm's Law, you will see a doubling of the current I, and the bulb will glow much brighter. I=2Vbatt/R This also assumes that the bulb's resistance (R) stays constant. However, the resistance in real light bulbs increases as they get hotter, so you will probably see a little less than 2x the current I when you double the voltage. Putting 2 batteries in parallel will not double the current I. The way to show that is with 1 battery driving 2 bulbs in parallel. Each of the bulbs will use an amount of current I=Vbatt/R, so the battery must double its current output. Good luck with the science project!
Thank you for being my physics teacher, Mr. Chan. May you Rest In Peace. ❤️
@Van Wang Appreciate Video clip! Sorry for butting in, I would love your initial thoughts. Have you tried - Franaar Shining Shape Formula (just google it)? It is a great one of a kind guide for revealing the secret to repair your electronic devices minus the headache. Ive heard some amazing things about it and my m8 finally got amazing success with it.
@@marianellaramirez3786 @Avery Callan you dudes are massive jerks.
@Adrian HD He passed away in the M/V Conception dive boat accident on September 2, 2019. Read his channel's description. Rest in peace :(
You explained it to me in five minutes better than my professors did. Great video.
true
Lucky you, my professor didn't even explained it properly.
Thank you for posting. This is the best and simplest explanation I've ever seen. If you ever expand it, please add the same test for the amperage output of a solar panel.
Thanks for the lesson Mr Chan. I wish there were more but know there won't be. You sound like an wonderful teacher
How much fire is acceptable when performing this procedure?
Hey this is the best explanation ever on ampere measuring! Slow accurate and really newbie proof!
FINALLY.....a Clear explanation for measuring Current/Amps ........Kudos!.............Z
Simple, quick, and useful. Thank you😊.
Thanks very much for this. Outstanding demonstration. Makes sense. You have to break the circuit to see the flow of current. I was very lucky I didn't break the meter before I saw this. Thanks very much.
Excellent , well done the best I have seen on UA-cam ! Thank you for posting. :-)
Thank you so much :) I never thought it should be connected in series to the circuit.
Love your vids and the quizzes . That is a really awesome thing so a person can actually obtain the information your supplying. 👍👍 ⭐️⭐️⭐️⭐️⭐️
Doesn't say why there is a resistor, or what size resistor, or what happens if there is no resistor. If I don't have a resistor and bulb, can I use a PC fan instead?
What is the resistor for? And what will happen to the multimeter if you don't connect a resistor in your example?
If he had done without the resistor, more current would then flow (higher reading would be measured on the multimeter).
But he used the resistor to protect the bulb, so it's likely that without the resistor, the high current and full voltage across the bulb would have blown the bulb.
I am glad I found this video. I may or may not have blown a fuse because of my ignorance.
I have a cheap multimeter with 20A fuse that can do 15 sec. max C test. A couple of times i have tested batteries under 20A (without a circuit) and the cable got hot, so i always do 4 sec test. My meter is still okay, your advice is also good
Great explanation. Short, crisp, and to the point. Thank you.
How much fire is acceptable when performing this procedure?
Wish I would have watched this before I fried my meter.DOOOOH!
You and me both i killed some very hard to replace fuses.
I have the same brand, strangly the fuse was intact. Upon closer look of the circuit I fried a tiny resistor (I could have re soldered).
Yeah guys I also have this problem. My multimeter just wanted to blow his fuse.
Same here hehhe
lol. me too. my red wire got hot and the insulation melted. i caught it just before the meter fried.
Great job. I'm sorry he passed away. Wanted to ask why its okay to put the multimeter probes on directly on a battery to measure voltage, but not in the amperage setting? Anyone welcome to chime in.
just learned in school, measure current going through, voltage across. Essentially when measuring voltage it’s okay considering you’re just measuring a potential different between two terminals. Thus measuring the open circuit voltage whilst putting a positive on hot, negative on ground.
When measuring current, putting an anmeter in parallel to a source, you’re shorting it, like connecting a wire, infinite current passes through the short and which drains your battery because V=IR.
I understood before I finished watching..thx man
Glad I watch your video first. Thanks for the info.
very concise and to the point, thank you
Thanks Bro! Your video tutorial is well explained and I just learned something new.
You've just answered my question :) I probably blown my fuse by now ^^ Thanks.
Thanks you dumbed it down perfectly for me ....thanks big
Finally a simple easy to understand explanation.
How much fire is acceptable when performing this procedure?
Thanks for making this video!
Very very good tutorial. Thumbs up!
Thanks a lot. (Delightful to watch real english electronics, bcoz indian electronics have flooded youtube. Not good)
More of them than us, world over that is.. And by far more in need of money.. So You-Tube pays per view, thus they flooded You-Tube with crap video's.. Most are not good or right, just in need of $7.23 per month from stupid-tube.. Sad..
Great Tips Good Stuff Very Clear Understanding 👍 Thanks!
Thank you.. It seems D) would actually measure the current through the resistor, but alter the circuit by shorting through the bulb.🙂
thanks saved me some time!
Now I get it....thanks for making it easy to understand 👍
Hi sir.....what is the Value of your Resistor use?
very nice tutorial.
Isn't the current decreases when it passes through the resistor?
This way we don't get the value of current of the battery
Thank You... Just the instruction I needed.
So are you telling me, I have to buy a bulb, a bulb holder and a resistor to measure the amps on a battery?...and how the heck do I know what resistor to use for all the different types of batteries....😖
Nice informative video thanks.
Thanks
Great work
Thanks. Just look this up. Very helpful video. 👍👍
best explanation, thanks you!
I am installing a video doorbell. It says my transformer has to be min of 16 vAC 10 VA, but how do I measure that? The meter only seems to measure DC amps. Why is that? Thanks.
This really helped me.. thank u very much
Strait!!! I subscribe!!! I like how this video is ran.
Great tutorial. Thanks!
Won't the current drop because of the load or Will it show the correct amps of the battery with load connected..?
How would u check currents (amperage) of a used Harbor Freight 25 watt Solar Panel with the same type of Ammeter .. is there a way to test the panel alone with no battery or load?
Thanks I have the same metter this is so helpful thanks alot
I've done this but it doesn't make a circuit and reads 0.00. Has the fuse blown previously with something I did long ago? I would have thought the mulitmeter just wouldn't work if that was the case
By the way got the test correct at the end.
EDIT: It is showing low battery on the multimeter... maybe that's why?
It is true. I blew up mines yesterday in a wall socket. It was wild 😂😂
Excellent video..👌👌
thanks I was closing to damage my multi-meter through attach the terminals to the power source (laptop charger)
hello Sir, can i do that in AC? I wanna know how much power my electric fan is consuming. thank you
He's 100% Correct. If you go Directly to the Pos and Neg Post with the Multimeter? You'll blow The Multimeter... Why I'm Telling you this is? Because I FREAKING FORGOT!!! THAT'S WHY!!! LOLOLOL Which is why I came to this Video... I haven't tested Amps IN OVER 20 YEARS... They say If You Don't Stay working with Electronics? YOU'LL FORGET STUFF...
I'm Proof "Positive" of that reminder. However, Luckily? I didn't blow The Multimeter. But The Wires caught hell... LOLOLOL!!! Great Video, and Thanks... I'll Be Bock...
Hi wat if I don't use a Resistor with the light ,, will that still work if I want to find the mAh of my 18650 lithium ion battery
This test shows the positive line used. Can the negative line be used?
How do we measure peak amps? How do we determine how much of a load the battery can handle? Larger watt bulbs?
very helpful video thanks !
does this multi meter need a battery? I do not get a display when its turned on
Hi, you mentioned it reads 0.15amps wht do other people say its actualy 1.5amps and otheres angain say its 150mAps?
Can I touch the meter the the battery if the battery is a 9V battery?
nice video understood the consept
I was just about to do the dumb thing, but the thought i should look up if i'm doing it right
So that's DC power, but for measure AC current in 110v or 220v house electricity, most have something connected on outlet running on, that's right ? eg: transformer, coffee maker or something like that, drawing power.
Okay, so you are using a "conventional view" of current flow. Actually in d-c circuits does not the flow come from the negative side of the battery? Should the set up and schematic show this?
how about measureing current not on a circuit ? i.e. generator;; motor..back up battery .. etc,
Will the battery be damaged if u connect direct to battery from leads?
God be with u sir
What if it’s a 12 volt battery do you move the settings to 20m and where do the leads go
Hi, i have a power supply 12v 20A connected to a step down convertor, i want to get a current of 5A using the convertor, like in your video where you used a lamp and resistor, what should i use so i can adjust the current from 20A to 5A?
Thanks
Nice video sir
hello sir, if i connect the multimeter after the led will the reading be different?
Nice Tutorial.
0.15A is 150mA right?
0.04 is 40mA right?
Nice!
Wish I knew this beforehand
It would me help if zoomed out so we could actually SEE the wiring!
Good job! But what I don't know now, is how to do this (measuring current) off of a solar panel. Could you tell me pls? I have searched and couldn't see your video on this. Thank you in advance.
First, a warning. Do not attempt this with a large solar array. Some of them put out many amps at several hundred volts. This type of system is extremely hazardous and not for amateurs. I will assume you are trying to measure a small panel, up to 12 V and a few amps. To do it with this type of meter you will have to disconnect the positive output wire that goes from the panel to the load. Configure the meter for the 10 A setting (assuming your panel puts out less than 10A), then connect the red (+) probe to the panel output, and the black (-) probe to the load wire you disconnected from the panel. The load must be connected to get a useful current reading. Be careful with this much current.
A better type of meter for measuring high power circuits is a clamp-on meter, which clamps around a single wire and does not require breaking the circuit or touching any live wires. Make sure you get one that measure DC current if you want to work with solar panels.
So what’s the resistor? Confused.
The 22 ohm resistor is in the circuit for two reasons: 1) to limit the current to the bulb, 2) as part of the video series "Measuring Resistance with a Digital Multimeter".
MrChanPhysics Thanks. Missed the other video. Great teacher! ✌️
Great info, thanks.So when measuring automotive devices I should know roughly how many amps the part puts out first?
Each circuit on a car is protected by a fuse. Each fuse is labeled with its maximum amperage. Almost every fuse in a car is at least 10 Amps, but the circuits generally draw much less current. The best use for the ammeter in a car is to find small "leaky" or "vampire" currents, meaning devices which are drawing current when you expect them to be off. A lot of electronics in modern cars (stereo, alarm systems, door locks) stay alive all the time and draw a small amount of current (10s of milliamps). So it can be useful to use the ammeter to find vampires if your battery is dying rapidly. For example, I had a car which drained the battery in a few days. It turned out that there was a small current drain in the power seat memory. One of the buttons was stuck "on" so it continued to draw current and kill the battery.
Using the ammeter on a powered-on device like headlamps or stereo is very risky since they will likely draw more than 10 Amps and blow the multimeter's fuse. It is less risky to use a voltmeter at the device to see if it is receiving power. See my video "Measuring Voltage with a Digital Multimeter".
You the man !
Very good
Hi , I'm trying to do an amperage test on my stanley Jumpit jumper starter pack . Jumpit Jump pack rated at 1000 peak battery amps and 500 instant starting power . ..... On my jump lead of my pack red & black clamp ....... would you walk me through the setting on my multimeter to read amperage out from my pack lead ? Greatly appreciated .... thanks
Great vid - thanks - looks like I have to replace my fuse now, lol.
I usually only deal with voltage/resistance for diagnosing car electronics, but I inherited a battery charger and wanted to test if it worked. Multimeter only supports 10A current, battery charger had a 2A (12v DC) option I wanted to test. I hooked it up in parallel to the battery on the loaded circuit, it sparked (the probes arched) a little when I connected the probes, no good reading, then unloaded, tried again, same results, now no sparks, lmao. Hopefully can replace that fuse. Should have watched this video first!!!
I'll replace the fuse and try it in series this time... For the 20A and 60A settings, I have to buy a new multimeter I guess. Any easier way to validate these? Seems most multimeters I find only go up to 10A on the current..
EDIT:
As a side note, if I test the voltage on the loaded circuit it's ~12.85 (typical charging output on a 12v auto DC circuit), but if I don't load it (if I test both alligator clamps that you'd connect to the battery) I only get ~9v. Is this normal? I would have expected to see 12.85 with or without a load. Thoughts?
To measure currents greater than 10 Amps, you will probably need an inductive-clamp type meter. It has a sensor that clamps around one wire and uses magnetic field to measure current. The clamp units do not require you to break the circuit, but the clamp can be clumsy to use in tight spaces. Make sure the one you use has capability of measuring both DC as AC (some only measure AC).
What would happen if you connect the negative lead(-) coming from the the amp meter/multimeter to the negative terminal(-) of the light bulb instead of the resistor(+) connected that's connected to the positive(+) terminal of the bulb? Would the amp meter/ multimeter still measure amperage drawn?
Just measures as negative if you reverse the leads.
If thats the case how can i measure my battary amp since its lebal is peeled off and missing?!
Does it matter if you connect it before our after whatever is drawing power??
Thank you very much.Nicee
All these UA-cam video show how to measure current on a simple circuit. Most of the time you will be trying to measure current in a wire so it becomes somewhat of a mess. For example, if you want to measure the current on a lamp, you would have to cut the wire just to get to one wire to get in series to measure it. If you're lucky your lamp will have one of the double wires where all you have to do is separate the two wires and put a clamp meter on it. If you don't have a clamp meter then you will have to cut one of the wires or both because you won't know which is the hot wire. These guys show you how to measure it but it is no where near a real world way to measure. Get's even more complicated when you are dealing with a big circuit where everything is grounded to a common wire.
Is the resistor necessary?
No, the resistor is not necessary for this task, but it is part of the same circuit that is explained in my Measuring Resistance and Measuring Voltage videos.
so this will just measure the current being drawn for the circuit right?
but what if we want to know the total current the power supply can put out? or is there no way to tell unless you know what the power supply is rated for already?
i have an old power supply harvested from a PC and i use the the 5v out to power some led lanterns i have hanging on my porch but now i want to add a USB to it to power a security cam , i am just afraid it might be too much current though
i read that current of the power supply should not excede double or 2 and half times what the load runs on , for exampe the camera comes with a 1A USB power brick and you can daisy chain up to 3 cameras off that one brick , but i will say 1A for the camera load , so if the PC power supply is rated at over 2.5A then will that be too much current and fry the camera?
HomeMade DIY HowTo Electronic
It would be necessary to not blow the light.
Maybe.
Unless it's a 12v light and battery.
You can only check DC amps with this unit no AC.
Can you check the amps of a circuit when it's not under load?
I have a 12v power distribution module for which each circuit can have the amperage set by a computer program. I lost the programming cable, so now I want to check how many amps each circuit is set to so I can be sure I wire a new accessory to a circuit with the appropriate amps set.
Or does the circuit need to be under load, and would I need to increase the load until the breaker tripped?
Current must be measured on a live, loaded circuit (unlike voltage , which can be measured on a live but unloaded circuit). Electric current is just like water flowing in a pipe; only when it runs is there anything to measure. If you do test the breakers for maximum load, please make sure that you don't burn down your shop.
Hi MrChanPhysics. I just watched your video. it looks great for me without any electricity or electronics background. I followed your tutorial piece by piece, setting exactly as you did BUT my multimeter read (1.) I am using 3AA batteries to operated a 3-led diodes of a PIR sensor light and I need to know the current so that I replace the batteries with a mobile telephone charger using the USB. Am I doing something wrong pls?
If the meter reads "1. " it probably means it is set to a scale too low to display the current. Try starting with the 10 Amp setting.. This may require you to move the red test lead to a different socket as I have shown in the video.
Nice video
I love those big batteries but you can't find them any more
hi Alls, may I know what value voltage and watt of the lamp that used in this video? I already tried and follow the step in this video with 24VDC 70W lamp and should be 2.9A by calculation right. but I only get 0.25mA. any idea?
how about testing current on circuit board like on laptop motherboard?
will it work the same if you disconnect the black lead and measure on that end?
Good question. Yes, it will measure the same because the current flows through all wires before returning to the battery in this simple circuit.
in that case, the negative terminal of the battery connects to the negative of ammeter and the positive of ammeter is connected to the negative terminal of bulb... am i right?
Urgent question for daughter's 3rd grade science project! We measure batteries in series and parallel connection. 2 AAA 1.5V batteries in Series go to 3V and supposedly the 1000 MAh stay the same, 2 AAA 1.5V in parallel stay at 1.5V but the Mah doubles to 2000, and 2 x 2 series connected in parallel go to 3V and doubles to 2000 MAh. I can measure the voltage increase or stay at same with the multimeter, plus I use a light bulb showing dimmer or brighter light, but how can I demonstrate the mAH increase for this purpose? I thought your video did that, but I get a reading of 0.12 and in parallel nothing changed. Using D or 9v I get the same readings when I though it would definitely be higher then the AAA battery.
Do I need something else to show this or can this only be measure over time? Just a simple proof of hypothesis to double the mAh in parallel would be needed. Thanks.
The current (mA) will not change between 1 battery or 2 batteries in parallel (as long as the batteries are fresh and the bulb is a low-power flashlight type). The bulb is a type of resistor (R). The "formula" for current (I) is
I=V/R. This is known as Ohm's Law. Since AAA, AA, C, D batteries all have the same voltage Vbatt, they will all supply the same amount of current I through a resistor or bulb R.
If you put two batteries in series, then you have doubled the voltage Vbatt and according to Ohm's Law, you will see a doubling of the current I, and the bulb will glow much brighter. I=2Vbatt/R
This also assumes that the bulb's resistance (R) stays constant. However, the resistance in real light bulbs increases as they get hotter, so you will probably see a little less than 2x the current I when you double the voltage.
Putting 2 batteries in parallel will not double the current I. The way to show that is with 1 battery driving 2 bulbs in parallel. Each of the bulbs will use an amount of current I=Vbatt/R, so the battery must double its current output.
Good luck with the science project!