How do you measure voltage from a power outlet with a digital multimeter?

Question

How do you measure voltage from a power outlet with a digital multimeter?

Answer 1

Just set your meter to AC Volts, and cram the probes into the two slots on the electrical outlet. Do not touch anything metal and you should be fine. It also helps to stand on a rubber mat, and make sure everything is dry.



JF is just a bluffer, not an electician - you can't get a negative reading from an AC outlet. It's AC!!



This is no more dangerous than, say, having a picnic in the middle of the freeway :)

Answer 2

First of all, if its a power outlet from your house ..... proceed.

If it is not from a house the voltage is likely higher and only a qualified electrician can legally do that.

The reason for this is that you need a CAT III meter to measure the higher voltages. Most meters from eg. Canadian Tire are only a CAT II or CAT I. So look at your meter and somewhere on it, there will be a rating from CAT I to CAT IV. If you are CAT II and above, proceed.

It all has to do with safety and how the meter was built.

Assuming you have a decent multimeter .......



1) Insure the leads are correctly inserted into the multimeter and are undamaged (the leads are the things you will be poking into the power outlet).



2) Turn the power (of the mulitmeter) on.



3) Different multimeters differ here how you would proceed. Usually there is a dial in the center that you can turn to select different things to measure. You want AC Voltage. Look for this symbol V~ . That is the symbol for AC Voltage. Set the dial to that symbol.



4) Some multimeters autoadjust. Others you have to adjust manually. If you have to adjust it, set it to a voltage higher than the one you expect to find. So if beside the V~ there are a bunch of number, like 10, 200, 600, etc. You would choose 200 (since housing should be around 120). It is likely your meter autoadjusts though so this is probably not a problem for you.



5) Now your ready to insert the probes into the outlet. It doesn't really matter which one you but the red and which one you but the black lead into. If its reversed you get a negative number. Just ignore it.



6) Hold the plastic portion of the leads and insert the probe ends into the outlet. (One each into the two verticle openings of the outlet).



7) Now you should be getting your voltage reading. Usually something between 118V and 125V.



Thats it. But stay away from your stove outlet and your washer and dryer. These are higher voltages and can be dangerous. Also stay away from your panel.



If you are checking to see if the voltage to the outlet is 0 because you want to work on it, check an outlet that you know to be live first (and you get aprox. 120V) just to make sure you meter is working before you trust the 0V.



Good luck.









Dude -- if u got ur leads reversed u get a negative reading

Answer 3

Assuming that a simple circuit means a resistive circuit with a power source ... Voltage: using a voltmeter, touch each probe to each side of the resistor. This means the voltmeter is in parallel with the resistance. Current: put an ammeter in series with the resistance. Each probe has to be on the same side of the resistor. There is an internal resistance that could affect your reading, but that internal resistance is large to minimize this effect. From a practical standpoint, you could use the equations below to calculate voltage or current, depending on what values are known ... Ohm's Law: V = IR, where the voltage is equal to the product of the current and resistance. So if you have a known supply voltage and resistance, you can calculate the current by solving the above equation for I: I = V/R.

Answer 4

If you're in the UK, which I think you might be, domestic voltage at all normal sockets - unless three phase - will be about 230 volts (+10% to -6% so 216 volts to 253 volts).



The problem you will have is trying to get your multi meter probes into the socket as modern sockets have spring loaded blocks to stop anything other than a plug getting in there. An electrician would remove the cover and check behind the socket if he or she really had to.



You could conceivably force the probes into the socket (the bottom two will guarantee a reading as they are neutral and live - the top is earth), but I would not recommend trying it!

Answer 5

if you have the correct meter you can just plug it in.



the correct meter depends on what you want to know.

RMS voltage?

or do you want to see the actually sinusoid waveshape?



either way....

prolly a bad idea.

Answer 6

This is dangerous, but if you are determined I would do the following:



Use an piece of extension cord that is cut. Strip and connect the wires to the clips on the DMM. Wrap your connections with electrical tape or use a wiring nut.

Once this is completed, turn on the DMM to AC mode, and plug in the plug on the end of the cord. May want to check the literature on the DMM to make sure this voltage level is safe for the DMM.



This should be a relatively safe way to test the AC voltage. It should be in the 110-120 VAC range.

Answer 7

Select meter to ac volts that cover the range of the outlet (UK 230V) and make sure the probes are in the correct sockets. There are a couple of interlock types of UK sockets that you will need to defeat. One of them requires something pushed into the earth to open the shutters, the other requires the probes to be pushed at the same time into live and neutral.



Here are your big dangers.



Electrocution from touching part of the probe exposed, or lead end not connected correctly to the meter.

Arc flash from incorrectly selected meter (i.e. set to current instead of voltage or probes in wrong sockets)



The above are assuming the meter, leads plugs etc are all in good condition and suitable for this purpose.



You are correct to avoid doing it if not necessary but if done by a competent person, with correct equipment for a good reason, the risk is acceptable.