Proster AC-4
Proster Non Contact Voltage Tester Pen User Manual
Model: AC-4
Brand: Proster
1. Introduction
This manual provides detailed instructions for the safe and effective use of your Proster Non Contact Voltage Tester Pen. Please read this manual thoroughly before operation and retain it for future reference.
2. Safety Information
Always prioritize safety when working with electrical systems. This device is designed to assist in detecting AC voltage, but it does not replace proper electrical safety procedures. Adhere to all local electrical codes and safety regulations.
- Do not use the tester if it appears damaged or is not functioning correctly.
- Always test on a known live circuit before and after testing an unknown circuit to confirm proper operation of the tester.
- This device is for AC voltage detection only. Do not attempt to measure DC current.
- Wear appropriate personal protective equipment (PPE), such as insulated gloves and safety glasses, when working with electricity.
- Keep out of reach of children.
- The tester is rated CE CAT. III 1000V / CAT. IV 600V. Ensure the voltage being tested is within these limits.
3. Package Contents
Verify that all items are present in the package:
- Proster Non Contact Voltage Tester Pen
- 1.5V AAA Battery (included)
- Operation Manual

Figure 3.1: Package Contents
4. Product Overview
The Proster Non Contact Voltage Tester Pen is a versatile tool designed for safe and convenient AC voltage detection. It features adjustable sensitivity, audible and visual alarms, an LED flashlight, and automatic power-off for extended battery life.

Figure 4.1: Proster Non Contact Voltage Tester Pen
Key Features:
- Non-contact Detection: Safely detects AC voltage without direct contact.
- Adjustable Sensitivity: Two ranges (48-1000V and 12-1000V) for various applications.
- Audible and Visual Alarm: Beeping sound and flashing LED indicate voltage presence.
- Live/Neutral Wire Distinction: Helps identify live and neutral wires at close range.
- LED Flashlight: Built-in light for working in dimly lit areas.
- Low-Voltage Indicator: Alerts when battery replacement is needed.
- Automatic Power-off: Conserves battery life.
5. Setup
5.1 Battery Installation
- Twist the cap at the top of the tester counter-clockwise to open the battery compartment.
- Insert the included 1.5V AAA battery, ensuring correct polarity (+/-).
- Replace the cap by twisting it clockwise until secure.
The low-voltage indicator will illuminate if the battery level is low, signaling that replacement is necessary.
6. Operating Instructions
6.1 Power On/Off
Press the green power button to turn the tester on. The LCD screen will illuminate. To turn off, press and hold the power button, or the device will automatically power off after a period of inactivity.
Video 6.1: Demonstrates the Proster Voltage Tester Pen in use, including power on/off, voltage detection, and sensitivity adjustment.
6.2 Non-Contact AC Voltage Detection
- Ensure the tester is powered on.
- Place the tip of the tester near the wire, outlet, or electrical component you wish to test.
- If AC voltage is detected, the tester will emit an audible beep, and the LED indicator will flash. The LCD screen will also show a visual indication of voltage strength (low, medium, high).

Figure 6.2: Null Wire vs. Live Wire Detection
When detecting a null wire, the tester will show a green LCD, and the buzzer and light will flash slowly. For a live wire, the LCD will turn red, and the buzzer and light will flash quickly, indicating higher voltage presence.
6.3 Adjusting Sensitivity
The tester has two sensitivity modes:
- Default Mode (Low Sensitivity): 48V-1000V AC.
- High Sensitivity Mode: 12V-1000V AC.
Press the "S" button to switch between sensitivity modes. High sensitivity is useful for detecting lower voltages or voltage through insulation, such as behind drywall.

Figure 6.3: Dual Range and Sensitivity Levels
6.4 Break Point Testing
To locate a break point in a live wire, move the tester along the wire. The tester will indicate voltage up to the point of the break and then stop indicating voltage beyond it. Use high-sensitivity mode for best results.

Figure 6.4: Break Point Testing
6.5 LED Flashlight Operation
Press the flashlight button (usually indicated by a light bulb icon) to turn the white LED illumination lamp on or off. This feature is useful for working in dark environments.

Figure 6.5: Backlight & LED Lighting in Dark Conditions
7. Maintenance
- Cleaning: Wipe the tester with a dry, clean cloth. Do not use abrasive cleaners or solvents.
- Storage: Store the tester in a cool, dry place away from direct sunlight and extreme temperatures. If storing for extended periods, remove the battery to prevent leakage.
- Battery Replacement: Replace the battery when the low-voltage indicator activates to ensure accurate readings.
8. Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| Tester does not power on. | Dead or incorrectly installed battery. | Replace battery, ensuring correct polarity. |
| No detection or inconsistent readings. | Low battery; incorrect sensitivity setting; interference from other electrical fields. | Replace battery; switch to high sensitivity mode; move away from strong electromagnetic fields. |
| False positives (detects voltage when none is present). | High sensitivity in an environment with strong electrical noise; proximity to other live wires. | Switch to low sensitivity mode (48-1000V); ensure proper isolation from other electrical sources. |
9. Specifications
- Model: AC-4
- AC Voltage Range: 12-1000V (High Sensitivity) / 48-1000V (Low Sensitivity)
- Frequency: 50Hz / 60Hz
- Alarm Mode: Sound and light alarm
- Live/Neutral Wire Distinction: Automatic
- Voltage Levels: Low, Medium, High (indicated visually)
- Flashlight: White LED
- Low-Voltage Prompt: Yes
- Auto Power-off: Yes
- Safety Rating: CE CAT. III 1000V / CAT. IV 600V
- Power Source: 1 x 1.5V AAA Battery
- Product Dimensions: 6.3 x 2.36 x 1.1 inches
- Item Weight: 2.82 ounces (80 Grams)
- Material: ABS and PVC
10. Warranty and Support
For warranty information or technical support, please refer to the contact details provided with your purchase or visit the official Proster website. Keep your purchase receipt as proof of purchase.
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