Measuring Current
Printed From: the12volt.com
Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=42294
Printed Date: May 02, 2024 at 8:19 PM
Topic: Measuring Current
Posted By: hurtado_roberto
Subject: Measuring Current
Date Posted: November 05, 2004 at 11:04 AM
Can you measure DC current with a clamp-on meter like the Protek 307? I looked at the specs and they say it has a 400 and 1000 A range for AC/DC. Does anyone know how you can measure the current without breaking the circut like these meters do it? If you can't measure DVA then what is the best way to accuratly figure out how many amps you're pulling from your amp with everything on. Fuses will blow fast so if you connect a few in series and keep taking some out until they blow you will figure out the peak amps you're drawing. If you use thermal breakers in series it will give you more of an RMS amp draw right. If you can read DVA with a clamp on DMM then which one do you suggest I should buy and where from. ------------- Poly Dollies
Replies:
Posted By: Teken
Date Posted: November 05, 2004 at 9:11 PM
The meter uses inductive measurment. The protek 307 will do what you are after.
If you require measuring very low mA current, this unit only measures down to 100 mA. Therefor, it cannot capture true parasitic current draws if that is what you are after.
Nice unit to use for the amplifer current draw, it will do the job your after for sure.
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Knowledge is power. But only if you apply that knowledge in a positive way, which promotes positive results in others.
EVIL Teken . . .
Posted By: flynntech
Date Posted: November 06, 2004 at 10:06 AM
Electricians and Installers alike favor the clamp on for it's ability to read current safely without breaking a circuit. Some meters come with a clamp and leads too, I'm not sure what the accuracy is, but it would do the trick for automotive use. Pay attention to the direction of the current (n/a with AC).
Posted By: Mad Scientists
Date Posted: November 07, 2004 at 12:37 PM
DVA = ? Clamp on meters are nice.. as always, if you can afford it, Fluke makes nice ones. Make sure that the clamp on meter you buy does DC.. some only do AC. For low level measurements <10amps or so, I just break the circuit and wire an ammeter in. Regards, Jim
Posted By: Teken
Date Posted: November 07, 2004 at 1:02 PM
Also, to follow up on Jim's reply. The resolution, and the accuracy (%) percentage is important.
BTW: Other meters use the Hall Effect principle, which is extremely accurate and versitile.
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Knowledge is power. But only if you apply that knowledge in a positive way, which promotes positive results in others.
EVIL Teken . . .
Posted By: hurtado_roberto
Date Posted: November 08, 2004 at 12:01 AM
DVA.. uppps. It was supposed to be DCA. I really don't think I need to get a meter with extreamly high accuracy in my opinion. In the 100-150 dollar price range I'm looking at there should be some good meters with good enough accuracy right. My electronics profesor suggested a Fluke meter. I'm not too experienced with hardware brands so I asked him about snap-on and he said that if they had one it would be an overpriced model from another company. Is this usually the case with snap-on? ------------- Poly Dollies
Posted By: Teken
Date Posted: November 08, 2004 at 3:35 PM
hurtado_roberto wrote:
I really don't think I need to get a meter with extreamly high accuracy in my opinion. In the 100-150 dollar price range I'm looking at there should be some good meters with good enough accuracy right.
The one you are looking at will do the job just fine.
hurtado_roberto wrote:
My electronics profesor suggested a Fluke meter.
Excellent suggestion on his part. I would ask you to look at any tool which you decide on, as a investment.
If you look at it this way, then the reason to spend money on anything, is more practical, and reasonable on the pallet & wallet.
hurtado_roberto wrote:
I'm not too experienced with hardware brands so I asked him about snap-on and he said that if they had one it would be an overpriced model from another company. Is this usually the case with snap-on?
Snap-On is an excellent brand. But as I stated before, the unit you are looking at will do the job perfectly. There are many other great companies who can do the job as well as Snap-On.
BTW: Snap-On does not manufacure any electronic equipment on site, it is either rebadged equipment, or is designed on their behalf based on their specifications. They do however manufacture and R&D all their basic hand tools.
------------- Knowledge is power. But only if you apply that knowledge in a positive way, which promotes positive results in others.
EVIL Teken . . .
Posted By: overworked
Date Posted: November 09, 2004 at 8:14 AM
Whats wrong with Ohms Law?
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Posted By: Teken
Date Posted: November 09, 2004 at 3:58 PM
overworked wrote:
Whats wrong with Ohms Law?
Ohms law will only tell you the static electrical flow, which is a educated guess based on the information given.
This assumes that the load does not change, but remains the same.
It will not however tell you the dynamic current draw in any given moment in time. Such as in a amplifier, based on volume levels.
ie, He could be drawing only 1 ampere, at level 1, when he wants to know what the actual live current draw is at various SPL which may be important to him. ------------- Knowledge is power. But only if you apply that knowledge in a positive way, which promotes positive results in others.
EVIL Teken . . .
Posted By: hurtado_roberto
Date Posted: November 09, 2004 at 7:03 PM
Are you refering to the true RMS ratings on meters? I looked at the protek and fluke clamp-on and they both stated true RMS current in AC but not in DC. So If I were to test the amps my alt is outputting then would it be fluctuation too much for me to read? Do you think these meters have a DCA RMS setting too and they state true ACA RMS because of the power factor in AC? ------------- Poly Dollies
Posted By: Teken
Date Posted: November 09, 2004 at 7:18 PM
The alternator would be supplying DC current, not AC. How about you explain to me exactly what you intend to do.
I could be totaly out to lunch on my replies. Since I was under the impression you wish to measure the DC current from the amplifier while it was under load.
Please correct me if I am wrong.
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Knowledge is power. But only if you apply that knowledge in a positive way, which promotes positive results in others.
EVIL Teken . . .
Posted By: hurtado_roberto
Date Posted: November 10, 2004 at 11:19 AM
I was refering to measuring DC current from the alternator underload. I was thinking that the current would be fluctuating with the bass. If I take a measurement of DCA what will it actually tell me? Will it be fluctuating considerably? Whould I need to get a meter that measures the RMS amps for this purpose? I could also measure the current on the speaker wires since that is in AC so I can size my wires accordingly. I'm not sure if it can really tell me the RMS ACA on the speaker cables because of the frequency variation compared to house current set at 60 hz in the u.s. So I think my main question is what should I be looking at too see if I need to replace my alternator with a bigger one? Will the amprage draw reach a limit which it can not go over. e.g. 90A on a stock alt. or will it overload it and go beyond the 90A? ------------- Poly Dollies
Posted By: Teken
Date Posted: November 10, 2004 at 5:16 PM
If your alternator is not able to keep up with the current demands, then the excess current will be drawn down upon the primary battery.
Please bare in mind there is a limit as to what either will do.
Some vehicle alternators will continue to supply the maximum current it can at all times, and in doing so will over drive and over heat the unit untill failure.
That in itself translates to a shorter service life for you, and the vehicle. You will also note that during this process of trying to supply the excess current that your morning start ups will gradually get harder and harder.
The reason being is that upon terminal failure of the alternator, the battery will be asked to supply the 20-30% of current that the alternator is not able to.
This then, begins the cycle of hard starts, and over / under charging from the alternator. So the primary battery will never be fully charged once you stop driving.
So bottom line is this: If you ground pound all day long, and you notice that your vehicle lights start to dim, or the vehicle starts to shake once normal loads are turned on.
ie. lights, blower, AC,
Then you need to upgrade your alternator with a H.O. one.
I would like to point out that unless you intend to listen to the exact same song over and over, and the volume is set to the exact same level over and over.
Then you will never know what the true current draw is for all music being played.
Question is does it really matter?? The maker has already written on the box what the maximum current draw is for the unit, given a specified load.
The two best things you could ever do for your vehicle and you, is to upgrade all the primary power and ground cables, and the alternator.
It is a investment that you will reap over and over for a very long time.
Just my thoughts on that
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Knowledge is power. But only if you apply that knowledge in a positive way, which promotes positive results in others.
EVIL Teken . . .
Posted By: Mad Scientists
Date Posted: November 10, 2004 at 8:00 PM
What I would suggest is installing a voltmeter to monitor chrging system voltage.. using an ammeter will only tell you how much current the alternator is putting out, it won't tell you if the battery is being charged. Using a voltmeter, I'd be concerned when the voltage drops below 13.0 Vdc. For the most part, as long as system voltage remains above 13.0 Vdc, your battery is being charged (or at least is not being discharged) Thoughts?.. Questions?.. Regards, Jim
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