You can do that if you have a shunt. An ammeter is basically a voltmeter that reads the voltage as it passes through a resistor (the shunt) with a known resistance. The ammeter then displays the amps as converted by Ohm's law.
Excellent video, this is just what I needed to better understand how a shunt and an ammeter work together to measure current. Thank you for making this.
I am not an expert. I do understand how many amps are being used and the importance of an amp gauge. Your video is very helpful. Thank you for being so simple in explaining it. Great video.
Austin, current is measured in amperes and voltage is measured in volts. With your multimeter set to read voltage (say the 20v setting), putting the red positive lead on the positive side of a battery and the black negative lead on the negative side will give you how many volts the battery is pushing out. With your multimeter set to the 10A setting, you can measure amperage in the same way but only for a VERY short amount of time or you will burn out the leads. Less than 10 seconds.
Thank you this was great video may who ever above bless you for 2 burned up shunt, now we all can benefit from your exprience to not house catch fire . I really apricuate shearing your exprience sir. Its keeps me my family safer because of you thank you sir🙏😀.
thanks man! very good of you to share your findings and knowledge. I want to do something very similar with a small power outage battery back. and you have helped me here.
Hey thanks for this, buddy, I have to adjust the voltage regulator on my '61 Oldsmobile and this is needed, in conjunction with a load tester. This was a perfect video because like you said, those little ammeters come with no instructions. Cheers from MN!
Thank you very much for that very short, precise and informative video. Had an ammeter for some time and had no idea how to wire it in. Again, thank you.
Very well illustrated, thank you. Going to build a "car cooler" on steroids but want the whole thing to be reliable and not kill an 80ah battery. All of the decent ammeters I looked at were not through design but required a shunt. Thanks for the video.
Yeah, there are very few ammeters out there that don't require you to run a shunt with it. The ones that don't are much more expensive and have one already built in.
My battery charger had the old ammeter with the sensor? encircled/wrapped around the negative cable. Is this a different system? Sorry I don't know what the terminology of the type I had. If I buy this style of ammeter with the shunt, as pictured in your video, does all the output have to pass thru the resistor, or does the resistor just protect the ammeter and allow unrestricted current to flow to the battery? Thanks in advance!
In order to measure the current, it has to pass through the shunt. The style shown in the video has a physical device with a known resistance that can measure it as it passes across the device. There are also devices called hall effect where there is a loop around the negative or positive cable that measures the current that way without being physically part of the circuit. However, I don't believe those are as accurate (I could be wrong).
So for my automotive application that I'm looking at doing something like this for, I would need a 12V 390A shunt and meter? I'm running a 390A alternator hooked up to a 3000 watt inverter that I pull around 1500 watts AC and wanted to keep an eye on my amperage and voltage draw.
Yes, you would need a shunt that can measure that much current. So the shunt needs to be at least 390A and needs to be matched to your meter. The meter will be designed to work with a specific resistance so it will be rated for a certain mV and the shunt needs to be the same rating. Be careful with that much current! That can start a fire almost instantly.
uma duvida! tenho um amperimetro analogico corrente ac alternada, 30 amper, e vou colocar em um aparelho bem forte, ( um chuveiro) seria nescessario colocar um shunt no amperimetro para guentar altas tensoes, ou pode ligar direto passando por ele sem frescura,? pode seguir a regrinha da soma de multiplicarr o valor de 220v x 30a = 6600w suportaria isso sem queimar o medidor, minha tensao aqui e de 220 volts?
I'm not sure on an AC ammeter. But you almost surely need an external shunt for 30A. Very, very few ammeters have an internal shunt that can handle 30A.
How do you wire an amp meter without a shunt on a car? I have a diagram that says the negative wire goes to the amp meter but the diagram isn’t detailed enough to explain exactly how the amp meter should be wired. Does the negative wire go to the negative terminal? What do I do with the positive terminal? It doesn’t say on the diagram?
Tks for sharing. o bough a HAU AMP 50a and do not want to use Shunt. The thing is the needle jumps to 50A when i plug a load of 1A. May the ammeter be deffective? tks
Thanks for the video. I couldn't find info any other place. Now my problem is finding a 10 amp / 1000 volt shunt. I think electronic instructors should caution their students about using them. All I have noticed is them saying to check the amps of a circuit connect the meter in a series.
I have a 100v/500amp I want to use on my welding leads. So I would put the shunt in the positive welding lead to measure the amps?. But measure the voltage between the the positive and negative welding leads?
The resistance is calculated for you. The shunt will have a rating on it with the value. Then you just need to match it with an ammeter that is calibrated for that resistance.
So what caused the other two to burn up? Was it because you didn't have the shunt? Do you really need a shunt? How would you hook this ammeter to a AC 240v circuit?
last we my boss used 1.5mm gauge wire of about 30 meters long to hook up to 40/5 voltmeter and Ct but at a distance of 1 meter we were getting 14A on the ammeter and 0 at a distance of 30 meters . so i quickly measured the voltage and i told him sir , theres is a voltage drop . He said we are measuring Amps and you are talking about voltage. I got confused and didnt know what i could use to eplain to him. Now i can thanks ......And thats a shunt
I recently purchased an old Triplett 0-5 Amp AC meter on E-Bay and was wondering if the AC meter requires a shunt before installing it in series with the AC house line I also have ordered an AC 0-150 volt meter to go with it. I guess if it does I'll play hell getting the info on the milliamps and meter resistance. The voltmeter should be a nobrainer though. Thanks, Ed Allen
+MedHawk Unfortunately, I don't know a lot about AC power so I can't answer about wiring in an AC amp meter. As for the volt meter it would wire up the same as in a DC system where you connect the positive lead to the positive wire and the negative lead to the ground wire.
An ammeter shunt allows the measurement of current values too large to be directly measured by a particular ammeter. In this case the shunt, a manganin resistor of accurately known resistance, is placed in series with the load so that all of the current to be measured will flow through it. In order not to disrupt the circuit, the resistance of the shunt is normally very small. The voltage drop across the shunt is proportional to the current flowing through it and since its resistance is known, a voltmeter connected across the shunt can be scaled to directly display the current value. Shunts are rated by maximum current and voltage drop at that current. For example, a 500 A, 75 mV shunt would have a resistance of 0.15 milliohms, a maximum allowable current of 500 amps and at that current the voltage drop would be 75 millivolts. By convention, most shunts are designed to drop 50 mV, 75 mV or 100 mV when operating at their full rated current and most ammeters consist of a shunt and a voltmeter with full-scale deflections of 50, 75, or 100 mV. All shunts have a derating factor for continuous use, 66% being the most common. Continuous use is a run time of 2+ minutes, at which point the derating factor must be applied. There are thermal limits where a shunt will no longer operate correctly. At 80 °C thermal drift begins to occur, at 120 °C thermal drift is a significant problem where error, depending on the design of the shunt, can be several percent and at 140 °C the manganin alloy becomes permanently damaged due to annealing resulting in the resistance value drifting up or down. Here is some good reading on this. en.wikipedia.org/wiki/Shunt_(electrical)
LDSreliance ill think about that some day but right now I'm a bit busy teaching electronics online. For right now I try keep it simple and point in the direction of correct knowledge.
Thanks for another explanation. To get an even more comprehensive understanding of it, you can remove the ammeter without affecting normal load performance? The shunt's purpose is to provide a measurable load to a small meter? Could you have a larger rated ammeter that is suited to measure current (say, up to 12v 20A) without a shunt and without affecting load performance? Like, I have a multi-meter that can measure up to 10A. Does that use a shunt inside somehow?
Justin, to my understanding ammeters measuring 10a and above (maybe even less) all use shunts. The problem is that with higher current comes higher temperatures and potential damage to the sensitive electronics. So they have to pull a small amount of current through a measured/calibrated shunt so that they don't fry it. I have seen small ammeters of like 1a that do not have an internal shunt.
I know the sellers online are very poor at stating whether a shunt is needed. I have bought about 6 of them and plan on testing them with a shunt first. The shunt will protect the meter from meltdown.
Is it possible to install a Shunt on the the Negative Side of a 110V AC. To 12V DC. Converter to read the DC. Battery voltage , Current and Amperage of the system ?
Thank You LDSerliance, I have a question, I'm trying to measure a 12-14DC Amp output with a multimeter that has a 10 Amp DC maximum tolerance. My question is the following: Can I use a shunt with a resistance or approximately 2 ohms and measure the DC Volts; once this is done, use Ohm's law to calculate the DC Amps? Once this is done, the DC amps that I measure using the shunt will be less than 10 amps. Then just work the backwards to find the DC Amps without using the multimeter. Would this work?
Each meter will be calibrated for use with a specific resistance shunt. You can calculate it yourself if you want but the manufacturer of the meter should have that information provided in the specs. Some meters have a small shunt built in to the meter itself if it is a really low amperage unit. If it handles lots of current, though, it will need a large external shunt like mine.
Hello LD I would like to install a volt/amp combo meter into my main electrical breaker box ( on the side of the main not inside the box it self) as I have a 30 amp breaker wired with a 10/4 gauge wire from a inlet box for my generator, do I connect the wiring from the meter into the breaker in the box and also do I need a shunt for that application Thanks Al
You always have to have a shunt for these type of meters. They can't handle that kind of current without one. You would need to run your load wires to the shunt and then into the electrical breaker box. If you have room you could actually mount the shunt inside the breaker box. Then you would have 2 small wires that would connect to the back of the meter itself (as shown in the video).
LD, Im" using 10/3 gauge into the box, for a 30 amp double pole, Im' going to put the shunt on the out side on a panel next to the main breaker as well as the meter, does the larger wires from the shunt feed into the breaker with ct on them, and the small wires feed the shunt and what gauge for the wires going into the box, and if I need to double the switches one for each side of the breaker board
Sorry for not seeing this sooner. The bigger gauge wires need to go from the source (solar panels or wind turbine or battery bank) to the load (inverter, charge controller, or whatever will be using the electricity). This will be the path of the electricity. Some small amount of the electricity will be diverted using smaller gauge wire from the smaller connections on the shunt to the ammeter. There should be a positive in and a positive out (-) connection on the back of the ammeter. Send me a private message if you still need help.
I have that kind of shunt,i callibrated it to 1mv/a ,btw where can i get those meter ? ,and i would recommend you to recallibrate the shunt since they're usually not callibrated properly out of the box
Good tip! I bought my ammeter on Amazon (www.amazon.com/Class-Accuracy-Square-Analog-Ammeter/dp/B00AO75HJ8/ref=sr_1_8?ie=UTF8&qid=1420907967&sr=8-8&keywords=ammeter+50a). It sounds like you know what you are doing so you should be fine ordering these. I would recommend ordering 2 of them at a time since they are so cheap and not packaged well. I have had 2 of them damaged in shipping (one broken glass but still worked, the other had internal damage and never worked).
Nope, the highest load I ever see is 20a but I wanted some room for expansion in the future so I got the 50a. There also aren't too many options in between like 10a and 50a.
Very Nice tutorial ordering a 100 amp/volt meter combo & shunt & definitely don't want to cook anything as I just destroyed one of my 50 amp power supplies accidentally.
@@LDSreliance Absolutely👍👍 I would have for sure blown the meter hooking it to negative! I'm using 4 gauge wire meshed & soldered to two 8 gauge wires going from shunt to the two 50 amp supplies.
No. The shunt protects the meter. The meter cannot handle that much current passing through it. It is not constructed with beefy wiring or circuitry and would fry in a second.
@@LDSreliance thanks for the reply 2 more doubts 1. Instead of ammeter can we use digital multimeter. 2. In some circuits having low load, i have seen ammeter directly in series, is it so?
Multimeter has the same problem. It cannot handle more than about 10A with its internal construction, usually. Yes, the ammeter and multimeter will have an internal current rating that it can handle being wired in series by itself without a shunt. But it is typically very low (10A or less).
hi, thanks for the vid, the only thing i cant figure out is what would be the load an a car be when only the ignition is on,( eg, were would i connect the load too presuming earth is just to earth ) would appreciate some help with this ? thanks again.
Hi, I have to replace a amp meter in a battery charger, I can't get the same replacement amp meter.( So I am using a amp meter with the same spec's ) The charger has a copper wire coming from the neg pole which rapted around the rear of the old amp meter & back to a cut out switch. ( I think this is how they could tell how much current was running through the unit & registered on the old amp meter ). Do I still need to use a shunt or can I just run a replacement wire to the new amp meter from the Neg pole to the amp meter back to the cut out switch & not use the shunt. Oh by the way does it matter if I ues Neg or Postive for the amp meter because the current is only going one way.
***** What you are doing sounds right but I can't say for sure. It sounds like the unit may already have a shunt in it. How many amps is this battery charger? Negative or Positive doesn't seem to matter much, although I have been told that the standard practice is to use negative (not what I showed in this video).
LDSreliance No shunt just a ( circuit braker switch ) not a cut out switch as I said. The battery charger is 30amp with a 240v power supply in Australia.
There has to be a shunt for that much current. Either it was internal in the previous ammeter or it is hidden somewhere else inside. It may not look like the one in my video. That is just one type of shunt. If not then I am afraid we are past my expertise level. Sorry!
***** There are two kinds of ammeters, one uses a shunt in series, as in the video, and the current is measured in parallel across the shunt. There is also an inductive ammeter. A clamp goes around one wire and current is measured through the wire without actually touching the wire. Google "clamp meter". You have an inductive meter, so, no shunt. Here is what I would do, depending on the charger. No guarantees though, do this at your own risk. Buy a cheap 0-10amp ammeter on e-bay for, $4-$5. Replace the uninsulated copper wire from the negative pole with a good hunk of insulated wire, and wire the ammeter in. Make sure you buy one of the 50amp ammeters with a shunt and wire it the way LDS shows. The ammeter should be on the 12v side of the circuit, so an ammeter that can handle 12v should be fine. There are some cool inductive ammeters with voltmeters that go up to 300v and 100amps on eBay for $10-$11 U.S. Yes, you can wire it on either the negative or the positive. I wire on the negative because electricity flows from negative to positive. If you want to have some fun with induction, buy a small transformer toroid magnet and a cheap LED. Take some old insulated network wire and wrap it around the transformer magnet, wiring it to the LED at the ends. Run one wire, either positive or negative through the center of the coil. If the LED doesn't light, reverse the LED. The LED should light up using induction, actually drawing power from the wire that passes through the coil, like a clamp meter or the ammeter in your old charger.
If I place an ammeter between the Solar charge controller and the battery to monitor the panel output would I need to do it via a shunt. As I see it any load will come directly from the battery not the solar controller and provided the ammeter is rated above max amperage of the panel no damage can be done if that makes any sense. Thanks
You are thinking like I did when I fried my first 2 meters. Unfortunately, the amperage rating of the ammeter means nothing. It is simply how much amperage the meter will read on the scale. It does NOT mean that is how much the meter can safely read before it blows up. The shunt is absolutely always necessary because the meter is calibrated to read the current across the shunt, which is a known resistance. If you want to measure amperage without using a shunt, try a clamp on meter rated for DC voltage. But you are going to pay a lot more.
LDSreliance Thanks for the prompt reply har har penny has dropped and that makes a whole lot of sense now. That's the problem being a DIYer trying to understand electricity using carpentry skills. Just found the parts on ebay guess where from meter and shunt for £6 so blow the expense :) order has gone in. Oh and thx for saving me 2 meters.
@@LDSreliance my machine is direct get A output because is battery discharge machine, last time I use precision shunt meter which prodigit 7550A , but I don’t have with me. So I have to use resistor shunt method , but since my machine already get Amp. So I am curious how to connect since I don’t have voltage supply for this ? So I connect +, - current to shunt resistor head and tail and middle is direct connect to + , - of multimeter I can get mV ? Is this correct ?
LDS, since the meter and shunt are essentially in parallel, can both sets of leads actually be on the meter and not the shunt ? I had a situation with a control panel the other day that was simple enough to do if this was OK but would be a rewire nightmare if not. I still have the "+" wire from the source going to the "+" side of the meter, the "-" wire from the meter going to the load. The Shunt is wired with separate leads from the meter in parallel. Gauge and meter specs match (0-25 ADC, 50 mV).
I stand corrected. I did some research and it looks like you can wire it with the load on the negative side. I don't know which is more accurate. Thanks for the tip! I learned something new today.
Does the 75mv mark mean that it can only measure currents with max. 75mv or does that mean something else? English is not my native language so I didn't realy understand
hello..! I made a testing rig to set the preset on some desire Current of my device. I want to replace my electric motor(10A, 220V, 2HP) by any other electric load. Can you suggest me which kind of load suites on my app.? Thanks.
you are measuring dc amps when inverter is truned on? How would hook up a dc amp meter , to measure amps, coming from your solar panels? Another question, measuring the dc amps going going too your battery bank? thanks
I thought you was supposed to wire negative from battery on big nut and wire incoming or out going current negative on the other large nut? I never hooked up positive power to my shunt only negatives on the large nuts.
What happens if you don't know which is the plus and which is the minus ? I built a unipolar generator - as part of an overunity experiment, preparedness for the coming insanity - and I wanna measure the amps output. I know the current forms between the axis and the rim, but I don't know which is which and I don't wanna damage the ammeter (wanna buy one of these analog ones). I tried with a 200A clamp meter and I didn't see anything.
If the shunt breaks then everything stops working. If the amps exceed the amp range of the meter then it will just peg the meter. It shouldn't hurt the meter itself but the shunt may be damaged.
Some meters do if they measure a small amount of amps. If it is more than about 10A usually they do not have an internal shunt because the shunt is very large and will require large wiring. Those small meters can't handle big heavy wires and the gauge would be massive. In that scenario you wouldn't want to run big heavy wires to where your meter is, either. You could just mount the shunt near where the wire runs to whatever device it goes to and then remotely mount the meter with small, cheap wire.
@@LDSreliance Thanks for the reply! If you are interested in seeing the vintage ammeter that I bought then go to imgur dot com slash obe6eG7 . I measured the resistance; less than 0.5ohm, so I think I can take it as having an internal shunt.
Can I just add a full bridge rectifier between the shunt and the “voltmeter” to sense AC? There might be some weird offset because the ems voltage is not the same as the average voltage right?
to measure amp from Solar panel, can I connect + panel to shunt and from shunt to solar + in solar controller and - panel goes directly to solar - in solar controller ?
Yes, it will work with any ammeter that needs a shunt. The specifications for the ammeter should say something like "75mv shunt required" or something.
What about the letters and numbers on the left side of the shunt at 0:26? Isn't that some form of calibration of the shunt which needs to match with the ammeter?
If you are wiring in an ammeter you will need a shunt. Unless you are measuring very small current (like 10A or less) then your meter might have an internal shunt. Make sure you read the fine print of the product.
It really doesn't matter. A lot of places insist on the negative side but I have searched for hours and never found a single source that can explain why it should be on the negative side. The reality is it works on either side.
You can put it on the negative side if you want. There may be some reason to do it. But I know for a fact it works on the positive side and I cannot find any reason that it is bad to do it like that.
Hey, I have a question. I thought that to meassure electric current you were supposed to connect the ammeter in series with the pass of current, bc in paralel you meassure the voltage. So I'm a little confused over here
Ivonne Monzón The Shunt is a kind of resistor and the meter is actually measuring the voltage in parallel across the resistor. If the resistor and meter are matched correctly, the voltage across the resistor is equal to the amperage. Look up Shunt (electrical) on Wikipedia. I just looked at the article and it is pretty good, today :-) that is.
