KCX-017 USB Voltage Ammeter Tester

The KCX-017 is a compact USB power tester designed to measure and display the voltage, current, and accumulated capacity of USB-powered devices in real time. It connects in-line between a USB power source (charger, power bank, or computer port) and the device under test, passing data through while simultaneously measuring the electrical parameters. The LCD screen shows voltage and current simultaneously, along with the accumulated capacity in mAh, allowing users to assess charger performance, cable quality, and power bank output efficiency without additional instruments.

The KCX-017 USB tester supports an input voltage range of 3V to 9V and a current range of 0.05A to 3.50A, with 0.01V and 0.01A resolution respectively. Voltage accuracy is specified at ±1%, and current accuracy at ±1–2% depending on the measurement range. The internal resistance of the tester itself is approximately 0.16Ω, which is low enough to have minimal effect on the measured circuit, and the line loss is approximately 0.1Ω. The display flashes when the voltage falls below 4.7V or rises above 5.3V, providing a visual warning of non-standard USB voltage.

A key practical feature is the capacity measurement function, which accumulates mAh over time to estimate the actual output capacity of a power bank or charger. The tester includes 10 memory slots for storing separate capacity measurements, allowing comparison between different devices or charging sessions. Data can be navigated with a single click (next) or double-click (previous), and cleared by holding the button for more than 3 seconds. The tester also supports Micro-USB cable quality testing by comparing the voltage drop when the device is connected directly versus through a cable—a smaller voltage difference indicates a better-quality cable. The module is factory-calibrated and requires no user adjustment, and it draws approximately 6.5mA during operation. It is a passive in-line measurement accessory—it does not generate power or charge devices; it only measures the power passing through it.