Radar method of measuring distance from a solid or liquid.
Radar distance sensors are measurement devices which transmit and receive high frequency radio waves (microwaves) to measure the distance to the surface of a liquid based substance.
Radar distance sensor technology transmits a high frequency electromagnetic wave pulse typically in the microwave spectrum, and receives the wave reflected off the surface of an object. The time taken for the microwave pulse to traverse the distance between the transmitting antenna and the target surface, and back again to the receiving antenna is measured.
The distance (d) between the radar distance sensor and the target surface can be calculated by dividing the time taken (t) by two, and multiplying that by the speed of light (c), i.e. d = c ∙ t / 2.
Unlike ultrasonic sensors, the performance of a radar distance sensor is not easily affected by temperature changes, humidity or vapour between the sensor and the target surface. This is because changes in air density only have a very small effect on the speed of electromagnetic waves. Also radar distance sensors can work in a vacuum, high pressures and high temperatures without any noticeable difference on measured transit time, so it can be used in applications where it is not possible to use ultrasonic based sensors.
Due to the high frequency electromagnetic waves used, it is possible to measure distance to a very high accuracy, as long as the surface is not too close to the sensor, where the pulse transit time becomes too small to measure precisely. This is called the dead zone, blocking distance or deadband, and is typically greater than an ultrasonic based device.
Since there is no contact with the object being measured, radar distance measurement technology can be used in applications where sensors requiring contact are otherwise prohibited. These sensors have no moving parts making them very reliable, and requiring very little maintenance.
Radar distance sensors are typically housed in a single assembly combining the transmitter and receiver antenna in one device.
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