🔌 Is Your Charger Safe? Test USB Output with a Multimeter

📱 Why You Should Test USB Chargers

Not all chargers are created equal. Faulty or poorly made USB chargers can cause:

• Overheating 🔥

• Battery damage 🔋

• Device malfunction 📴

• Fire hazards 🚫

Testing your charger’s voltage and current output can help you determine:

• Is it safe to use?

• Is it delivering the correct power?

• Is your device charging efficiently?

Let’s learn how to check it with a multimeter.

🧰 What You’ll Need

• A digital multimeter (e.g., BSIDE S11, SH7, or S30)

• A USB load tester OR a USB breakout board (for safe probing)

• Your USB charger + cable

• Optional: a device for real-load test (e.g., smartphone)

⚠️ Safety Tips

• Never short the USB terminals

• Avoid touching metal tips while connected

• Use USB testing boards if possible to avoid damaging ports

🧪 Step-by-Step: Test USB Output with a Multimeter

🔋 Step 1: Set Your Multimeter to DC Voltage Mode

• Turn the dial to DC Voltage (V⎓)

• If using a manual meter, select the 20V range

🧷 Step 2: Connect Your USB Charger

1. Plug the charger into a power outlet

2. Insert a USB cable

3. Expose the wires (or use a USB breakout board)

USB color coding (typical):

• Red = +5V

• Black = Ground

• White/Green = Data lines (not used here)

📏 Step 3: Measure Voltage

1. Touch the red probe to the red wire (+5V)

2. Touch the black probe to the black wire (GND)

3. Check your multimeter reading:

🔌 Step 4: Measure Current (Optional)

To check current (amperage), you need a USB load tester or connect the multimeter in series—which is not beginner-friendly.

An easier solution:

• Use a USB power meter that displays current & voltage (you can promote this as an accessory too!)

📊 Bonus: Compare With Other Chargers

Test different chargers with the same method to compare:

• Fast chargers (5V/2A, 9V/2A, 12V/1.5A)

• Older/cheap chargers (5V/0.5A)

You’ll see that high-quality chargers maintain stable voltage under load, while cheaper ones drop quickly or spike dangerously.

🧰 Why Use a BSIDE Multimeter?

BSIDE multimeters like S30 or SH7 offer:

• Auto-ranging DC voltage mode

• Dual display (for faster comparison)

• Portable, accurate, beginner-friendly

• Budget-friendly tools for everyday use

✅ Conclusion

Testing your USB charger’s output with a digital multimeter is a fast, reliable way to check safety and performance. If your voltage is too low or too high, it's time to replace your charger—before it harms your device.