Today, we’re diving into the basics of reading AC and DC voltage. How To Read Simple AC And DC Voltage. Whether you’re a beginner or brushing up on your skills, this guide will walk you through simple testing methods and show you why it’s critical to always double-check your readings.
How to Read AC and DC Voltage Safely and Accurately
Why You Should Use More Than One Testing Method
When reading AC and DC voltage, never rely on just one method. It’s essential to double-check your results using at least two tools. This redundancy helps prevent dangerous mistakes. As an electrician, I’ve been shocked more than once because I trusted a faulty tool.
Voltage Testing Tools
Here are the three basic tools we’re using:
- Multimeter – A versatile tool for measuring voltage, resistance, and more.
- Voltage Tester (Voltic) – A simple device that lights up when it detects voltage.
- Plug-in Circuit Tester – Great for confirming if an outlet is live and properly wired.
You don’t need to spend a fortune — all of these can be purchased at your local hardware store for $30–$40 or less.
Demonstrating Each Tool
We start with the voltage tester. Just turn it on and stick it into the outlet. If it lights up, your outlet is live — and so is the connected wiring.
However, don’t just take its word for it.
Next, we plug in the circuit tester. This confirms the outlet is indeed live. If you were planning to do any electrical work, you’d know to turn this circuit off first.
The Multimeter: Pros and Pitfalls
Using a multimeter requires more care. One major issue is damaged leads. If your leads are bent, broken, or worn out — like the ones I showed in the video — you risk a false reading. That could mean thinking a circuit is dead when it’s actually live. Always inspect your test leads before using them.
How to Test AC Voltage
- Set your multimeter to AC voltage (look for the squiggly line symbol).
- Plug in your leads securely.
- Insert the leads into the outlet slots.
We’re getting a reading of 123 to 124 volts — exactly what we expect from a standard wall outlet.
Now, double-check with a second method (like the plug tester or voltage pen) to confirm your reading. This is your safety net.
The Danger of Broken Test Leads
If your multimeter leads are damaged, your reading could be completely wrong. Imagine testing a circuit that’s actually live — but your multimeter says it’s dead. That’s a recipe for a nasty shock.
Always double-check. Always inspect your gear.
Reading DC Voltage
When measuring DC power, like from a battery, your options are more limited. You’ll typically use a multimeter. Some mechanics or techs might use a light tester that clips to the negative side and probes for power, but that’s less common.
How to Test DC Voltage
- Set your multimeter to DC volts (look for the straight line with dots).
- Press the Select button to switch from AC to DC mode if your meter has one.
- Connect the red lead to the positive terminal and the black lead to the negative.
For example, testing a 12V battery might show 12.5 volts. If you reverse the leads, the screen will show a negative voltage (e.g., -12.5V) — that just means you’ve swapped the polarity.
Final Thoughts: Always Use Two Methods
If there’s one key takeaway from this post, it’s this:
Never trust just one tool to tell you whether a circuit is live.
Use two methods. Double-check your work. It could save your life.
If you’re interested in more videos on using meters, testing fuses, or other electrical basics, check out our video library. Don’t forget to like and subscribe or visit our website (link in the description) for a fully searchable video archive.
Stay safe — and see you next time!