Eddy Current
Senior Member
How can you tell the difference in AC and DC out in the field? If it has a neutral its AC right?
How to tell AC/DC in the field
- Thread starter Eddy Current
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ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
With a DVM.
Eddy Current
Senior Member
What is that?
RichB
Senior Member
- Location
- Tacoma, Wa
- Occupation
- Electrician/Electrical Inspector
Digital Volt Meter
Eddy Current
Senior Member
How can you tell with a meter? If you read nothing on the DC setting then its AC?
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
Or you could switch it to the AC setting.
Eddy Current
Senior Member
So there is no way to tell without a meter just by looking? I guess you could look at a tag or something couldn't you?
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
131014-1154 EDT
Use a compass or magnet if current is flowing.
Voltage only use a tongue test, it tastes different. Frog leg kick. Test with your fingers. Try electroplating. Electro sensitive paper or organic material. A diode and incandescent lamp. A PM DC motor. An AC induction motor. Find an electro-sensitive person that can detect radiation from smart meters. Possibly a divining rod. Anything else you might imagine. Study arc discharge. Listen for hum in an iron cored coil. Connect a headphone.
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Use a compass or magnet if current is flowing.
Voltage only use a tongue test, it tastes different. Frog leg kick. Test with your fingers. Try electroplating. Electro sensitive paper or organic material. A diode and incandescent lamp. A PM DC motor. An AC induction motor. Find an electro-sensitive person that can detect radiation from smart meters. Possibly a divining rod. Anything else you might imagine. Study arc discharge. Listen for hum in an iron cored coil. Connect a headphone.
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Eddy Current
Senior Member
What about the neutral part would that matter?
- Location
- Massachusetts
How can you spot a neutral?
White conductors are grounded conductors but are not always neutrals.
With grounded DC systems you will have a white that is not a neutral but is DC.
To answer your original question I read the labeling on the equipment the circuit is connected to.
- Location
- Placerville, CA, USA
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- Retired PV System Designer
... at either end.
gar
Senior Member
- Location
- Ann Arbor, Michigan
- Occupation
- EE
131014-1343 EDT
Edison and his crew invented the three wire system with a neutral to reduce the cost of copper required.
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Edison and his crew invented the three wire system with a neutral to reduce the cost of copper required.
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- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
ggunn
PE (Electrical), NABCEP certified
- Location
- Austin, TX, USA
- Occupation
- Consulting Electrical Engineer - Photovoltaic Systems
You could look for a sign that says "THIS IS A DC CIRCUIT", I guess. I am having a bit of trouble understanding where you are coming from with this question. Wire is wire. Whether it's AC or DC depends on what it's connected to. A white or white tagged wire usually means it is a grounded conductor, but that has nothing to do with whether it's AC or DC. Other than that, the wires (AC or DC) could be any color.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
If you don't have a label to read and also do not have a voltmeter, just get out the compass you always carry and place it near one wire.
If when you turn on the load the needle vibrates it is AC. If it rotates to a new constant position, it is DC.
K8MHZ
Senior Member
- Occupation
- Electrician
Edison invented a 3 wire DC system using lights in series, which did reduce the amount of wiring needed. Our 3 wire AC system is similar to Edison's DC system, but does not use series loads.
I personally think Edison was a scoundrel, and I am not fond of him getting credit he doesn't deserve. I don't think he deserves credit for inventing the 120/240 volt split phase AC system we now use.
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K8MHZ
Senior Member
- Occupation
- Electrician
If you have a no-contact tester and it indicates, it's AC.
If you have an Ideal solenoid tester, it will tell you if it's AC or DC by which of the LED's light up.
If the wires are on a transformer, it's AC.
If the wires are on a battery, it's DC.
Motors and incandescent lights can be either.
And, as others have said, using a volt meter will work, too.
An oscilloscope would answer the question in a single measurements but I accept that not all of us carry one around with us.
But most of us would have a multimeter these days.
DC is most often derived from an AC source so has some ripple.
Set the meter to DCV and measure the voltage.
Do the same on ACV and measure the voltage.
If the second measurement greatly exceeds the first, you have AC.
But most of us would have a multimeter these days.
DC is most often derived from an AC source so has some ripple.
Set the meter to DCV and measure the voltage.
Do the same on ACV and measure the voltage.
If the second measurement greatly exceeds the first, you have AC.
kwired
Electron manager
- Location
- NE Nebraska
I was going to say that then you got it with the last post before I got here.
Eddycurrent, you also may be familiar with the supply and can tell pretty easily what you are dealing with just because of what you see there.
If utility supplied, there is like over 99% chance it will be AC. If it is separately derived, but from utility supply, it is still AC unless there is rectifier involved. On site produced power - you must know something about the source before you can tell for certain.
Eddy Current
Senior Member
I didn't know DC couldn't be transformed. This brings up another dumb question, do volt tracers work on dc power?
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