Discovering How to Measure AC Current for a 120V Device | Tips and Tricks

In summary, the conversation discusses how to measure the current draw of a 120V AC device using a multimeter or a clamp meter. The use of a clamp meter is recommended as it is more convenient and safe, and can provide a more precise measurement. The conversation also mentions the potential risks of using a multimeter and suggests looking for a clamp meter at a local store for around $50.
  • #1
eberg
10
0
Hi Everyone,

I'm new to the forum, this is a great place to dig around and do some reading.

My first question is:
I want to read the current draw (amps) of a 120V AC device (standard wall plug). I've worked with DC quite a bit but rarely with AC. Can I just probe the plug spades with a multimeter to read the current in an AC circuit, or how could I test this?

Thanks
 
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  • #2
What kind of device are you talking about? It would be inconvenient to use a conventional multimeter to measure the current of a device since the multimeter would have to be connected in series with the device.

You would have to cut one wire of the cord and insert the meter in series at the break.

A clamp meter would be useful in this case. This is a meter that will take current readings without the need to break the circuit. It clamps on the wire and uses electromagnetic induction to measure the current. Fluke makes good clamp meters. Of course, fluke makes nice meters in general.

http://www.fluke.com/products/specifications.asp?SID=0&AGID=0&PID=30405

Are there any ratings on the device you want to take a reading from?
 
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  • #3
That sounds a little easier than using a multimeter, I wasn't even sure if AC could be measured with a multimeter in the way you described. It's not convenient or real safe, but it's nice to know it can be done that way.

Thanks for the advice on the clamp meter, that would be the best. I don't own one, but may be able to get one from work that I could borrow.

I would like to use it like on a drill for example, where as the load increases I could measure it quantitatively using the increase in amperage.
 
  • #4
Glad to be of help. I definitely wouldn't recommend cutting your power cord to measure current. Who would want to anyway? .

Besides, a typical multimeter might not be able to handle the current depending on what you are measuring. The one I have here is only rated up to 10A.
 
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  • #5
If you have highly inductive load like powerful electric motor, then handheld Meter in series can a) fail, b) give bs readouts. Be careful.
Clamp meter could even give more precise measurement besides being both more convenient and safe.
 
  • #6
Thanks a lot guys. I found some clamp meters online for fairly cheap. I'll check out some local stores, looks like I should be able to pick one up for around 50 bucks that is still decent quality.
 
  • #7
Originally posted by wimms
Clamp meter could even give more precise measurement besides being both more convenient and safe.
That's the best option. I have an extension cord with the wires separated for easy clamp-on for testing 120v loads.
 

What is AC current and why is it important to measure it?

AC current stands for alternating current, which is the type of electrical current that flows in most household devices. It is important to measure AC current because it allows us to monitor and control the amount of electricity being used, which is essential for safety and efficiency.

What equipment is needed to measure AC current for a 120V device?

To measure AC current for a 120V device, you will need a digital multimeter, which can measure both voltage and current. Make sure the multimeter is set to measure AC current and has an appropriate range for the expected current flow.

How do I measure AC current for a 120V device?

To measure AC current for a 120V device, first turn off the device and unplug it from the outlet. Then, insert the multimeter's prongs into the correct ports (usually labeled "amps" or "mA") and connect them to the device's power cord. Turn on the device and read the current measurement on the multimeter's display.

What are some common tips for measuring AC current?

Some common tips for measuring AC current include making sure the multimeter is set to the correct range, using proper safety precautions, and taking multiple measurements to ensure accuracy. It is also important to check the device's manual or specifications to determine the expected current range.

Are there any safety precautions to keep in mind when measuring AC current?

Yes, it is important to take proper safety precautions when measuring AC current. Always make sure the device is turned off and unplugged before connecting the multimeter. Wear protective gear, such as gloves and safety glasses, and avoid touching exposed wires. If you are unsure about the process, it is best to consult a professional electrician.

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