There are two types of Speed sensor namely Inductive type– Proximity sensor / proximity switch / proximity probe. Also can be used to measure distance, vibration of an object. And another is Magnetic type – Magnetic pick-up sensor or MPU.
Inductive Proximity speed Sensor working principle:
Inductive Proximity sensor creates a magnetic field from their detection face, when a body moves towards or passes through the sensor magnetic field, eddy current is created in that target body. Then this eddy current in the target body generates its own magnetic field. The magnetic filed of the target body distorts the magnetic field of the sensor. This change in the sensor’s magnetic field triggers its output voltage, which is a speed signal.
When Inductive Proximity speed Sensor Output is high it becomes nearly equal to the supply voltage. And then the switch output goes to zero volts.The on-off nature of the output of a proximity switch produces a square wave.
Facts of Inductive Proximity Sensor
Power supply to the sensor is required.Used to measure “Slow” surface speed,used as Speed sensor, Limit switch/Position sensor. Output is constant.
Magnetic pickup unit speed Sensor working principle:
Magnetic pickup unit speed Sensor works same as describe above. The only difference is that a permanent magnet replaces the inductive circuit set up. Thus power supply is not required in Magnetic Pickup unit speed sensor.
The MPU makes use of a “stray magnetic field” and no provision for return magnetic circuits or paths is necessary. Any device which produces a dynamic discontinuity of magnetic material in the field of the pickup will produce an electrical voltage.
The magnetic pickup produces a voltage output when any magnetic material moves through the magnetic field at the end of the pickup. With any given speed and clearance conditions, a maximum power output will result when the field is filled with a relatively infinite mass of magnetic material at one instant and a complete absence of such material the next.
Magnetic pickups can usually works with magnetic materials made gear or shaft. Nonmagnetic materials, such as aluminum, brass, and some stainless steels, will not excite the magnetic pickup.
Facts of Magnetic pickup unit speed sensor
Suitable for High surface speed, No Power supply needed, Output Variable to speed.