Test 12v Amps?

[RogerD]

How do you test 12v amps?

I have a 12v cigarette lighter extension with heavy gauge neg / pos wires.

Could I just split them apart and put a meter with a clamp on the positive wire?

If that will work. Should I start the vehicle, put the clamp around the wire and zero out and then turn on the device?

Also, is there an inexpensive meter you could recommend. The cheapest meter I have seen that does 12v amps is like $85.

I have a kill-a-watt meter for AC, just not sure how to test DC.

 

[John61CT]

That is what better / medium ones cost

https://www.amazon.com/gp/offer-listing/B005VUBGZW

Uni-T UT203 or 210E

Mastech Ms2108a, MS2115A, MS2109A
https://www.amazon.com/gp/aw/d/B000BT422W

https://www.amazon.com/bayite-6-5-100V-Voltmeter-Multimeter-Amperage/dp/B013PKYAV6

 

[Trebor English]

The one I have is

https://www.amazon.com/Analyzer-Dig...236_SY340_FMwebp_QL65&keywords=amp+hour+meter  

I use 1/4 inch spade quick connects for my wiring so I put those on the meter.  The input side is male, output side is female.  Normally if I'm not using it for anything else I put it between the solar panel and the solar charge controller.  As the PWM goes on and off it keeps track of the amp hours.  

To measure current using a volt meter run the current through a resistor and measure the voltage drop.  I use a .001 ohm resistor like this one:  

https://www.amazon.com/DROK-Accurac...t+resistor&dpPl=1&dpID=41czo2ANe2L&ref=plSrch  

One millivolt is one amp.  200 amps is 200 millivolts, .2 volts.  

One foot of AWG #10 wire is .001 ohms.  I have used that to measure starter motor current on a DT466 school bus.  .5 volts is 500 amps.

 

[Knit]

I made my own 12v meter from this https://smile.amazon.com/gp/product/B001B6N2WK/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1 and a 12v extension cord. I cut off the male and female ends of the 12v extension cord and connected them to the input and output sides of the meter. I’ll post a picture of it in a couple of days.

I’m using it to test the power consumption of various Cpap machines hooked up through 12v cords. Using a Kill-a-Watt for AC power consumption. I’ll post the numbers when the experiment is complete.

 

[DannyB1954]

Not all clamp around inductive amp meters will work with DC. As a matter of fact most will only work with AC.

 

[John61CT]

Pretty sure all the ones mentioned so far do measure DC amps.

The cheapest ones might only handle 10-20A or so, maybe not as precise.

Fluke's 376 FC is the one to look out for, sometimes under $250 on eBay used but recently calibrated.

But the $50-80 ones listed are good emough for most purposes.

 

[jonyjoe303]

dc wattmeter (Digital Monitor LCD Watt Meter 60V/100A DC Ammeter RC Battery Power Amp Analyzer) you can find on ebay for less then 12 dollars, just splice in between battery and load.

 

[John61CT]

With the cheapie inline ones, check to see if you need 2-way

cut their max rating in half, do not get close to that for long, and if you feel them getting hot, disconnect for 5 min.

Buy spares

Anderson plugs inserted at your various measuring points makes them easy to move around.

Do not expect accuracy for battery monitoring.

 

[DannyB1954]

Pretty sure all the ones mentioned so far do measure DC amps.

People are not obligated to buy what has been mentioned. My advice stands. Must you always try to find fault with whatever I post? You are an expert at everything even when you are wrong.

 

[tx2sturgis]

I'm wondering if this is a one-time test, multiple tests, or a need to have a more permanent in-line solution.

The word 'test', to me, means a brief reading, then the need for testing is concluded.

A simple automotive ammeter will read amps, in a general way, up to around 60 amps. It wont accurately display anything under about 5 amps, but might be good enough for a few simple tests. 

Expect to pay around $20 and you will need to hook it up inline with the current being measured.

For testing multiple devices accurately, and verify current in DC cables, you probably do need a good AC/DC clamp-on ampmeter.

.

 

[tx2sturgis]

That is what better / medium ones cost

https://www.amazon.com/gp/offer-listing/B005VUBGZW

Sinometer?

SIN-o-meter?

Please don't get that thing anywhere near me!!

 

[John61CT]

People are not obligated to buy what has been mentioned. My advice stands. Must you always try to find fault with whatever I post? You are an expert at everything even when you are wrong.

I have no idea I've ever quoted you before, not something I track, no need to get personal, I just clarified that your warning was not of concern wrt the recommendations made.

 

[Knit]

I made my own 12v meter from this https://smile.amazon.com/gp/product/B001B6N2WK/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1 and a 12v extension cord. I cut off the male and female ends of the 12v extension cord and connected them to the input and output sides of the meter. I’ll post a picture of it in a couple of days.

I’m using it to test the power consumption of various Cpap machines hooked up through 12v cords. Using a Kill-a-Watt for AC power consumption. I’ll post the numbers when the experiment is complete.

Here is what it looks like.

Sent from my iPad using Tapatalk