A speed sensor is a sensor that converts the rotational speed of a rotating object into an electrical output. Speed sensors are indirect measurement devices and can be manufactured using mechanical, electrical, magnetic, optical, and hybrid methods.
Based on the different signal formats, speed sensors can be divided into two types: analog and digital.
Most output pulse signals (approximately sine waves or rectangular waves). Methods for measuring rotational speed using pulse signals include: frequency integration (also known as F/V conversion, the direct result of which is voltage or current), and frequency arithmetic (the direct result of which is a number).
In automation technology, rotary motion speed is frequently measured, and linear motion speed is also often indirectly measured through rotary speed. A DC tachogenerator can convert rotary speed into an electrical signal. The tachogenerator requires a linear relationship between the output voltage and the rotational speed, as well as a steep output voltage gradient and good stability over time and temperature.
Speed measuring machines are generally classified into two types: DC and AC. Rotary speed sensors are in direct contact with moving objects. When a moving object contacts the rotary speed sensor, friction causes the sensor's rollers to rotate.
A rotational pulse sensor mounted on a roller sends out a series of pulses. Each pulse represents a certain distance value, thus allowing the linear velocity to be measured. In an electromagnetic induction type, a gear is mounted on a rotating shaft, with an electromagnetic coil on the outside. Rotation occurs due to the passage of light through the gear teeth, generating a square wave voltage, from which the rotational speed is calculated.
The rotary speed sensor does not have direct contact with the moving object. A reflective film is attached to the edge of the impeller blades. As the fluid flows, it drives the impeller to rotate. Each rotation of the impeller transmits light through an optical fiber, generating one electrical pulse signal. The speed can be calculated from the number of detected pulses.
