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# how to measure AMP?

## how to measure AMP?

#1
10-31-02, 07:25 AM
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how to measure AMP?

i got a 12V DC adapter. but i don't know how many AMP in there. i use multimeter to measure it but it won't tell me anything. anyone know how to measure a AMP please help me. thanks

#2
10-31-02, 07:37 AM
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Amps are a function of load. With no load, there are no amps. If you short it out, there will be a lot of amps for a brief period of time before it burns itself out.

Most of the time, the maximum amps that a device can handle before destroying itself are shown on the device. This is something designed in. If there is no such label, I don't believe there is any way of finding out.

Amps aren't something that is "in there."

#3
10-31-02, 07:49 AM
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so there is no way to find out? but can u apply the V=I/R to find out the current? also how to measure the R (resistor) , is just by switch the multimeter to Resistor and measure it as measure Voltage?

#4
10-31-02, 08:22 AM
masterjoe
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As an EE, here's how we do to measure the current carrying capability of a circuit.
You have to make a little apparatus with different resistors connected in series. At the end of the run(DC only), connect an ammeter IN SERIES with a circuit.
Connect it to the DC source, and ammeter will show you the amount of current running through the load.
Either add or delete resistors to change the value of the resistance to either decrease or increase the current flow.
You mentioned the formula V=I/R. That's not correct.
It's called Ohm's law, V=IxR. According to it, resistance and amperage are indirectly proportional. More loads, less current flow....less loads, more current flow.

This is the only way to find the exact current carrying capability of a circuit.

Because it involves a rather complex test, most electrical equipments(wires, X-formers....) specify the current ratings on their labels.

#5
10-31-02, 08:58 AM
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oh just because i moved house and i lost a adapter for my LCD monitor. and it 12V DC 5AMP. that's all i know about it. then i bough adapter which 12.6V 6Amp but the pic it on for few sec and it turn off? that's why i need to know how to measure the current of the adapter i just bough. Or may be my monitor dislike other adapter.

#6
10-31-02, 09:57 AM
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Join Date: Sep 2002
Location: welland ontario
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Check the adapter again. Is ti 12.6 volt AC or DC. It makes a difference. Also if it is DC make sure the polarity is correct. The center could be positive or negative.

#7
10-31-02, 12:33 PM
Bazooka227
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Who makes the LCD monitor and which model is it?

#8
10-31-02, 03:58 PM
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it's call COMPAL CM870, it's the same as ASTRON CM870 as i found on a website. well m pretty sure is a DC because it says at the back of the monitor input 12V DC, 5A . it's made from TAIWAN.

#9
10-31-02, 07:56 PM
jlbos83
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The monitor is DC, but do we know for sure about the power supply? joed's ideas make sense. Assuming it is working, and is DC, the new supply should be fine.

#10
10-31-02, 09:00 PM
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yup everything is okie now it's working now but the picture is blury and jumping ...
Hey one more question. how to know is the adapter is regular voltage. i mean if it says 12V then it 12V althetime.

#11
11-01-02, 06:21 AM
masterjoe
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Multimeter

That's when you can use your multimeter.
Connect the X-former to the unit, plug it into the wall, turn it on and measure the voltage across center conductor(+) and an outer conductor(-) of the X-former output jack.