Digital LED Tachometer RPM Speed Meter - 4-Digit Blue Display with Hall Proximity Sensor

Specifications

• Display Type: 4-Digit LED (Blue illumination)

• Measurement Range: Typically 10 to 9999 RPM

• Sensor Type: Hall Effect Magnetic Proximity Sensor (NPN Normally Open)

• Sensor Shape: Threaded cylinder with blue sensing cap

• Wiring (Sensor): 3-Wire Cable (Brown, Black, Blue)

• Power Requirement: DC Power (Usually 8V - 24V DC)

• Refresh Rate: ~3 times per second (depends on speed)

Key Applications and Projects

• Lathe and Milling Machines: Upgrading manual machine tools with a digital RPM readout to ensure optimal cutting speeds for different metals and tooling.

• Motor Test Stands: Monitoring the exact rotational speed of brushed or brushless DC motors under various load conditions.

• Conveyor Systems: Tracking the speed of drive rollers to synchronise automated assembly lines.

Unlock New Capabilities (Project Evolution)

• Precision Upgrade: Install the small neodymium magnet directly into a recessed, epoxied hole on your spindle pulley to create a permanent, vibration-proof speed tracking system.

• Panel Integration: Use the snap-in clips on the back of the grey housing to flush-mount the blue LED display directly into your master control box for a clean, professional aesthetic.

Package Includes:

• 1 x 4-Digit Blue LED Panel Meter

• 1 x Hall Effect Proximity Sensor (with mounting nuts)

• 1 x Small Round Triggering Magnet

• 1 x Multi-colour Connection Harness

FREQUENTLY ASKED QUESTIONS (FAQ)

1. How does this tachometer work? You mount the small round magnet to a rotating part. The threaded sensor watches for that magnet. Every time the magnet passes the sensor, the meter counts it and calculates the RPM.

2. What color is the display? This specific model features bright blue LED digits.

3. Does the magnet polarity matter? Yes! Hall effect sensors are polarized. If the meter reads "0000" while spinning, flip the magnet over so the opposite pole (North or South) faces the sensor.

4. How close does the sensor need to be to the magnet? Typically, the blue tip of the sensor needs to be within 1mm to 10mm of the magnet for reliable detection.

5. What are the three wires on the sensor for? Standard industrial wiring applies: Brown is VCC (Positive), Blue is Ground (Negative), and Black is the Signal output.

6. How do I mount the display? The grey plastic housing has flexible tabs on the top and bottom, designed to snap into a rectangular cutout on a control panel.

7. What is the maximum RPM it can display? Because it is a 4-digit display, the maximum theoretical readout is 9999 RPM.

8. Can I use this on a car engine? While technically possible if you mount a magnet to the crank pulley, it is designed primarily for electric motors and industrial machinery, not direct automotive ignition systems.

9. Does it measure zero RPM? When the shaft stops spinning, the display will return to "0000" after a brief timeout to indicate no movement.

10. Do I need to program or calibrate it? No, it works out of the box. It assumes one magnet pass equals one revolution.

11. Can I use multiple magnets to get faster updates at low speeds? While you can put multiple magnets on a shaft, this basic meter cannot divide the signal mathematically. Putting two magnets will cause the meter to display double the actual RPM.

12. Is the sensor waterproof? The cylindrical sensor body is generally rugged and sealed against splashing, but the open wire ends and the back of the display panel must be kept dry.

13. How do I mount the sensor? Use the included metal nuts to secure the threaded cylindrical body to an L-bracket near your rotating shaft.

14. What voltage does it need? These kits typically require a DC power source between 8V and 24V.

15. Will it work if the sensor is covered in oil? Yes, magnetic Hall effect sensors are impervious to dust, oil, and non-magnetic grime, making them ideal for dirty machine shops.

16. What happens if I lose the magnet? You can replace it with any strong neodymium magnet, but remember to test which pole triggers the sensor.

17. Is the display easy to read? Yes, the 4-digit blue LED provides excellent contrast, especially in low-light environments.

18. Can the sensor touch the magnet? No, physical contact at high speeds will destroy the sensor's blue cap. You must leave a small air gap.

19. What is the included wire harness for? The multi-colored wire harness plugs into the back of the panel meter to connect the unit to power and the sensor signals.

20. Is this suitable for a wood lathe? Absolutely; it is one of the most popular upgrades for variable-speed wood and metal lathes.