1. Introduction
The BENETECH GM8906 Digital Contact Motor Tachometer is a portable, high-precision instrument designed for measuring rotational speed (RPM) and linear velocity. It features a high-definition LCD backlight display, automatic shutdown, and low power indication for user convenience. The device utilizes a high-sensitivity contact probe combined with an upgraded microprocessor and internal components to ensure accurate and reliable measurements across various applications.
2. Safety Information
Please read this manual thoroughly before operating the device to ensure safe and proper use. Keep this manual for future reference.
- Do not attempt to disassemble or modify the device. Unauthorized modifications can lead to malfunction or injury.
- Ensure the device is used within its specified operating environment (temperature and humidity).
- Avoid exposing the device to extreme temperatures, direct sunlight, or high humidity.
- Keep the device away from strong electromagnetic fields.
- Handle the contact probe with care to prevent damage.
- This device is not waterproof; avoid contact with liquids.
- When replacing batteries, ensure the device is turned off and use the correct battery type and polarity.
- Dispose of batteries and the device according to local regulations.
3. Product Components
The BENETECH GM8906 tachometer typically includes the main unit and several interchangeable contact heads to suit various measurement needs.
- Main Unit: The handheld device with LCD display and control buttons.
- Contact Heads:
- Small Conical Tachometer Head
- Large Conical Rotating Head
- Cylindrical Tachometer Head
- Linear Speed Head
4. Setup
4.1 Battery Installation
The GM8906 requires 2 AAA 1.5V batteries (not included). To install:
- Locate the battery compartment on the back of the device.
- Open the battery cover.
- Insert 2 AAA batteries, ensuring correct polarity (+/-).
- Close the battery cover securely.
Note: Shipping regulations often prohibit the inclusion of liquids, powders, and dry batteries. Please purchase batteries separately.
4.2 Attaching Contact Head
Select the appropriate contact head for your measurement task. Gently push the desired head onto the metal shaft at the top of the tachometer until it is firmly seated.
5. Operating Instructions
5.1 Device Overview
- Menu Key (MEM): Used to access memory functions (MAX/MIN/AVG/LAST values).
- Start/Close Measurement Key (Power/Measure): Press to start or stop measurement.
- Switch On/Off/Backlight Key (Lightbulb/Power): Press to turn on/off the device or toggle the backlight.
5.2 Power On/Off
- Press the Switch On/Off/Backlight Key to turn the device on.
- The device will automatically shut down after 60 seconds of inactivity to conserve battery life.
- To manually turn off, press and hold the Switch On/Off/Backlight Key.
5.3 Taking Measurements
The GM8906 is designed for contact measurement of rotational speed (RPM) and linear velocity. It supports measuring objects such as engines, fans, washing machines, and ships.
- Select Appropriate Head: Choose the contact head that best suits the surface or shaft of the object you are measuring.
- Power On: Turn on the tachometer using the Switch On/Off/Backlight Key.
- Start Measurement: Press the Start/Close Measurement Key.
- Contact Surface: Gently press the selected contact head against the rotating part of the object. Ensure firm and stable contact for accurate readings.
- Read Display: The RPM or linear velocity will be displayed on the LCD screen.
- Stop Measurement: Release the Start/Close Measurement Key to stop the measurement.
5.4 Data Hold and Memory Functions
The device supports holding the maximum, minimum, average, and last measured values.
- While a measurement is active, press the Menu Key (MEM) to cycle through MAX, MIN, AVG, and LAST readings.
- The current reading will be held on the display until the measurement is stopped or a new measurement is initiated.
5.5 Video Demonstration
Watch this video for a visual guide on operating the BENETECH GM8906 Digital Contact Motor Tachometer:
6. Maintenance
6.1 Cleaning
- Wipe the device with a soft, dry cloth. Do not use abrasive cleaners or solvents.
- Keep the contact probe clean and free from debris to ensure accurate readings.
6.2 Storage
- When not in use for extended periods, remove the batteries to prevent leakage.
- Store the device in a cool, dry place, away from direct sunlight and extreme temperatures.
- Keep the contact heads organized and protected from damage.
6.3 Battery Replacement
When the low battery indicator appears on the LCD, replace the batteries promptly to ensure continued accurate operation.
7. Troubleshooting
| Problem | Possible Cause | Solution |
|---|---|---|
| Device does not power on | Dead or incorrectly installed batteries | Replace batteries, ensuring correct polarity. |
| Inaccurate readings | Loose contact with object; dirty probe; damaged probe | Ensure firm contact; clean probe; replace damaged probe. |
| LCD display is dim or flickering | Low battery power | Replace batteries. |
| Device shuts off unexpectedly | Automatic shutdown activated; low battery | Press any key to reactivate; replace batteries if low. |
8. Specifications
| Feature | Detail |
|---|---|
| Model Number | GM8906 |
| Type | Tachometer (Contact Type) |
| Brand Name | BENETECH |
| LCD Screen Display | 5-Digits large screen, Backlight |
| Range | 0.5-19999 RPM |
| Resolution Ratio | 0.1 RPM (0.5-999.9 RPM), 1 RPM (above 19999 RPM) |
| Accuracy | ±(0.05% + 1dgt) |
| Sampling Rate | 1 second/time |
| Measuring Distance | 50-500 mm |
| Time Base | Quartz Crystal |
| Automatic Shutdown | After 60 seconds of inactivity |
| Low Battery Indication | Yes |
| Memory Function | MAX/MIN/AVG/LAST values |
| Operating Environment | 0~50°C (32~122°F); 10%~90% RH |
| Storage Environment | (-10)~50°C (-14~122°F); 10%~75% RH |
| Battery Included | No (Requires 2x AAA 1.5V) |
| Certification | CE |
9. User Tips
- For best accuracy, ensure the contact head is perpendicular to the rotating surface and applied with consistent, gentle pressure.
- When measuring linear speed, ensure the linear speed head is aligned with the direction of movement.
- Always check the battery level before critical measurements to avoid interruptions.
- Utilize the memory function (MAX/MIN/AVG) to capture peak performance or average speeds over time.
10. Warranty and Support
BENETECH products are manufactured to high-quality standards. For warranty information, technical support, or service inquiries, please refer to the contact information provided with your purchase documentation or visit the official BENETECH website. Keep your purchase receipt as proof of purchase for warranty claims.
