Using a Fluke Multimeter to Measure Computer's Current Consumption: A Comprehensive Guide

Question

Hello. I apologize in advance if this is in the wrong section, so I couldn't find an answer to my question. I have a Fluke multimeter (sorry in advance for the size of the picture, but I had problems with downsizing, so I didn't want to lose quality, since it's already poor - How...

artaa · Accepted Answer

Plug the probe cable into the 10A plug and measure the current.

niutat · Accepted Answer

Hello, insert the black plug into the 10A≈ socket and set the meter to A≈, connect the meter in series with the measured circuit, this will be an approximate measurement only.

MACIEK_M · Accepted Answer

Set the switch to ~A. leave the black wire in COM, the red one in the 10A socket (Fused). The current read from the display (in amperes) you multiply by 230V (you can also measure the voltage) and you get the power in VA (W). Just be careful - mains voltage !!!

otapi · Accepted Answer

just first switch the red cable as you have in the photo ;] otherwise the light will go out ;]

luqpp · Accepted Answer

black -> COM, red -> 10A, set the meter to A ~ (AC). Cut the power cable (one wire) and connect in series with a meter. With this measurement, it does not matter where the red and where the black wire will be. As the colleague above wrote, this will only be an indicative measurement.

jb111 · Answer

A bit more maybe? I'm green at this. Red plug at 10A, black where it is, ammeter option - AC ~ ? Which wire does the ammeter connect to? edit. ok, so the black probe in 10A, I leave the red one in place? Approximate measurement? Accuracy of 10W?

niutat · Answer

Black at 10A, red where it is. If you want to get an accurate measurement, use a kWh meter at home.

jb111 · Answer

I see that opinions are divided, I don't want to damage anything. Which wire does the ammeter connect to? If I know the exact mains voltage, will I achieve an accuracy of 10W?

jb111 · Answer

Ok, thanks everyone for your help, one more question, regardless of which way I put the meter? (black/red probe in the side of the socket/receiver, it doesn't matter?) Can someone write how accurate such a measurement can be?

niutat · Answer

With AC, it doesn't matter how you plug in the meter, I don't know about accuracy, unfortunately.

otapi · Answer

it doesn't matter which way, if it was direct current it doesn't matter either, at most you'll get a result with - (minus) because the current will flow in the other direction

niutat · Answer

The fact, in these meters it does not matter, my mistake. (I grew up on analog : wink

otapi · Answer

one more question, do you want to measure how much your computer draws from the mains or from the power supply? e.g. you have a 300W power supply and you want to know how much spare you have to connect the GForce 9600 GT to your computer? I will say change the power supply ;] but in such a situation to measure the consumed power, you would have to connect to all outputs from the power supply connected to receivers (boards, disks, etc. and count and if so, take the correction if it's some cheap power supply (modecom or something like that) for -(minus) 50-80W in relation to what is written ;]

W.P. · Answer

As already mentioned by a colleague note you will get the correct result using the electricity meter reading. Measuring the current with ammeters will give you some result, but it will be highly falsified. The instrument you are going to use is designed to measure undistorted (sinusoidal) voltages or currents. A computer power supply strongly deforms the current waveform, even when it is equipped with a PFC or APFC system. So the meter will show something there, you multiply it by the voltage value and you will think that this is the power drawn from the network by your computer.

tzok · Answer

What you measure will be apparent power (and strongly falsified, because the meter does not have a TrueRMS converter), because you do not know and are not able to measure the power factor.

jb111 · Answer

It all worked out. The goal was to measure the current consumption of the entire computer set. For the curious - E2180, HD4850, 1 disk, 2 DDR2 chips, a 22 LCD monitor takes about 140W at rest. Under stress, after overclocking to 3.2GHZ, the max consumption of the sets is 280W. Thank you for your help and best regards.

tzok · Answer

How did you measure it? ammeter? If so, the real (active) power consumed by this set is about 20-30% less than the measured one (in idle state, especially if the power supply has PPFC, even less).

jb111 · Answer

Yes, I measured it with an ammeter. The power supply has active pfc and efficiency above 80% - Corsair 450. If you say so, I'm all the more happy

kondensator · Answer

You're not so happy. This meter does not have the True RMS function so the correct results for alternating current will only be given when you turn on a purely resistive load (old type iron, heater, light bulb). Was:

jb111 · Answer

Do cheap wattmeters (energy consumption meters) from Allegro ~ PLN 50 have True RMS measurement options?

otapi · Answer

I have a question a bit OT but I have to ask because I see that experts are speaking. I know that power measurement is difficult and there are several powers (not going into acoustics powers anymore) but for example, I have a 70W universal laptop power supply (on the converter), I set it to 12V, connect a 12V 50W halogen bulb and the inverter does not start, it is overloaded, the light bulb blinks but does not light up, I connect 35W and it is ok ... question: the nominal power of the power supply is lower than declared by the manufacturer, is it a matter of the type of load?

W.P. · Answer

capacitor Thank you so much because sometimes hands go down... tapi During the initiation of the lighting process, the bulb filament heats up from the ambient temperature to approx. 2.5 ÷ 3 thousand °C. During this time, the resistance increases more than 10 times. So if you connect a 50W bulb, the power supply sees a load 10 times greater (500W) at first. And now it's all crashing down on time. The designer of the power supply has specified a certain time after which the short-circuit protection is to operate. At the same time, current flows through the filament of the bulb, heating it up. Bulb resistance increases (load current decreases). If the load decreases within the set time, the current controller will not cut off the power supply. If the process of lighting the bulb takes too long (50W), the power supply will turn off. Added after 2 [minutes]: They do not have. You need to allocate about PLN 300-400.

kondensator · Answer

Colleague lost one zero... Although simpler and cheaper by half, there are also (WORTH READING). Even cheaper than PLN 300, and yet well indicating the desired value, will be a set: a used electricity consumption meter (single-phase from about PLN 30) + a watch (from about PLN 5). The results calculated from their indications will be many times more reliable and closer to the truth than those read from miracle meters for PLN 30...300 with alle... / with Conra...

[Solved] Using a Fluke Multimeter to Measure Computer's Current Consumption: A Comprehensive Guide

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