1. Introduction
The Keweisi KWS-V20/V21 USB Current Voltage Capacity Tester is a compact and versatile device designed to measure various electrical parameters of USB power sources and connected devices. It can accurately display voltage, current, accumulated charge capacity (mAh), and elapsed time (H). This tester is an essential tool for evaluating the performance of USB chargers, power banks, and charging cables, making it suitable for personal use, laboratories, and factories.
2. Product Overview
The KWS-V20/V21 USB Tester features a clear digital display and a simple interface for ease of use. It is available in two models: KWS-V20 (typically blue casing) and KWS-V21 (typically red/black casing).
2.1 Components
- USB-A Male Connector (IN): Connects to the power source (e.g., charger, power bank, PC USB port).
- Reset Button: Used to clear accumulated capacity (mAh) and time (H) data.
- USB-A Female Port (OUT): Connects to the device being charged or tested.
- Voltage Display (V): Shows the real-time voltage in Volts.
- Current Display (A): Shows the real-time current in Amperes.
- Capacity Display (mAh): Shows the accumulated charge capacity in milliampere-hours.
- Time Display (T): Shows the elapsed time of the measurement in hours and minutes.
3. Specifications
| Feature | Specification |
|---|---|
| Model | KWS-V20 / KWS-V21 |
| Material | Plastic |
| Color (KWS-V20) | Orange (translucent) |
| Color (KWS-V21) | Red (translucent) |
| Voltage Measurement Range | 4-20V (Accuracy: ±1%) |
| Current Measurement Range | 0-3A (Accuracy: ±1%) |
| Time Measurement Range | 0-99 Hours |
| Dimensions (Body) | 59mm (Length) x 25mm (Width) x 13.5mm (Height) |
| Total Length (with USB plug) | 72mm |
4. Setup
The Keweisi USB Tester is designed for plug-and-play operation, requiring no additional power supply or complex installation.
4.1 Connecting the Tester
- Locate the USB-A Male Connector (IN) on the tester.
- Plug the USB-A Male Connector (IN) into your USB power source (e.g., wall charger, power bank, computer USB port). The tester's display should light up, showing the current voltage.
- Locate the USB-A Female Port (OUT) on the tester.
- Connect your device (e.g., smartphone, tablet, USB fan) to the USB-A Female Port (OUT) using its charging cable.
5. Operating Instructions
Once connected, the tester will automatically begin displaying real-time data.
5.1 Reading the Display
- Voltage (V): The upper left part of the display shows the current voltage supplied by the power source.
- Current (A): The lower left part of the display shows the current being drawn by the connected device.
- Time (T): The upper right part of the display shows the elapsed time since the measurement began, in hours and minutes.
- Capacity (mAh): The lower right part of the display shows the accumulated charge capacity in milliampere-hours. This value represents the total charge transferred to the device over time.
5.2 Resetting Data
To reset the accumulated capacity (mAh) and time (T) readings, press the Reset Button (labeled 'RESET' on the tester, component 2 in Figure 1). This is useful for starting a new measurement cycle or for testing the capacity of a different device.
6. Maintenance
- Cleaning: Use a soft, dry cloth to clean the tester. Do not use liquid cleaners or solvents.
- Storage: Store the tester in a cool, dry place away from direct sunlight and extreme temperatures.
- Handling: Avoid dropping the tester or subjecting it to strong impacts, as this may damage the internal components or the display.
- Moisture: Keep the device away from water and high humidity to prevent electrical damage.
7. Troubleshooting
7.1 No Display / Device Not Charging
- Check Connections: Ensure the tester is firmly plugged into the power source and the device is securely connected to the tester.
- Verify Power Source: Test the power source (charger, power bank) directly with your device to confirm it is functional.
- Check Cable: Try a different USB cable between the tester and your device.
7.2 Incorrect Readings
- Loose Connections: Ensure all connections are snug.
- Device Compatibility: While highly compatible, ensure your device and charger are within the tester's specified voltage and current ranges (4-20V, 0-3A).
- Reset Data: Press the reset button to clear previous readings and start a fresh measurement.
7.3 Display Flickering
- Unstable Power Source: The power source might be unstable. Try a different charger or power bank.
- High Current Draw: If the connected device is drawing current close to the tester's maximum (3A), some flickering might occur under heavy load.
8. User Tips
- Evaluate Charger Quality: Use the tester to check if your USB wall chargers or power banks are delivering their advertised voltage and current. A significant drop in voltage under load or very low current might indicate a faulty charger or cable.
- Monitor Power Bank Capacity: When charging a power bank, you can use the accumulated mAh reading to estimate how much charge is being put into it, helping you understand its real capacity.
- Identify Bad Cables: A common issue for slow charging is a poor-quality USB cable. By comparing current readings with different cables, you can identify and replace inefficient ones.
- Check Device Charging Rate: Observe the current (A) reading to see how fast your device is actually charging. This can vary depending on the device's battery level and charging technology.
9. Warranty and Support
This product is covered by a standard manufacturer's warranty against defects in materials and workmanship. For warranty claims or technical support, please contact your retailer or the manufacturer directly. Keep your purchase receipt as proof of purchase.