It measures the current and voltage of the power supply unit with a USB port.tou can Plug and play, no extra power required. The voltage and current will show a circle. Small size, simple and easy to carry.

Specifications:
Possible range: 4 - 30V, 0 - 3A.
Resolution: The voltage is 10mV and the current is 10mA.
Error range: voltage <±1%, current <±2%.
Full-scale voltage drop: 200mV.
Operating temperature: 0 - 60 ° C.
Color: transparent, blue

Not only a Multimeter but also a protector: our drop USB digital meter is a practical test tool that can be used to measuring Voltage current temperature capacity energy time via your electronic devices simultaneously furthermore, this gauge has Auto shut down function when it is over Voltage, under Voltage or fully charged, effectively protect your mobile devices
• Multiple protections, Intelligent and safe: this ideal USB multiple detectors owns over-voltage, under-voltage, over-current, under-current and under-current delay time five protections it will monitor real-time input Voltage/current intelligently when the input Voltage/current is over/under the limit Voltage/current, the input will be shut D automatically to protect the panel and the mobile device you are connecting
• Hurry to get yours: we offer you 100 percent risk-free satisfaction guarantee to let you buy with confidence this excellent USB pocket USB protector which can help you reduce the damage during charging do you love your phone, hurry to get one to protect it
• Effortless operation: this pocket USB digital Multimeter achieve one-button operation you can easily rotate the screen, switch capacity unit/data set, clean capacity, shut D screen by the Key in the back of the meter and it is portable and lightweight, you can monitor the output voltage and current of mobile charger cables, power use of raspberry pi or Arduino board anytime and anywhere you want
• Clear OLED display, low power consumption: USB monitor adopts 0 91″ high-quality OLED display, which has advantages of high brightness, high resolution, Stable and Clear digital display and low power consumption it has bright white font and black background, Clear and soft to read, even in dark condition