4-Digit LED Tachometer with Hall NPN Sensor - M12 Cylinder, 8-24V DC

The tachometer display unit itself operates on a wide-range power supply of 8 to 24 volts, either AC or DC. The integrated Hall NPN sensor also requires a DC supply within the 8-24V range (specifically 6-36V DC according to its datasheet). Ensure your power source can provide the combined current draw of approximately 40mA for the display plus the sensor's operational current.

The sensor uses a standard three-wire configuration: the brown wire connects to the positive supply voltage (V+), the blue wire connects to the ground (V- or GND), and the black wire is the NPN open-collector signal output. This black output wire will switch to ground (sink current) when a magnetic field is detected, providing a pulse to the tachometer's input.

This Hall effect sensor is designed to detect permanent magnets. It has a nominal detection distance of 10mm. For RPM measurement, you must attach a permanent magnet (e.g., a small neodymium magnet) to the rotating shaft or wheel. The sensor will generate one pulse per revolution as the magnet passes within 10mm of its sensing face.

Yes, this tachometer features non-volatile memory. When power is removed, the last displayed RPM or count value is automatically saved and will reappear when power is restored. This is useful for maintaining operational data across power cycles without resetting to zero.

The counting range is 0-9999 RPM. The limiting factor for high-speed measurement is the Hall sensor's switching frequency of 320 kHz, which is extremely high and far exceeds the pulse rate of most mechanical systems. Therefore, the 9999 RPM display limit is the practical constraint for reading the value.