Radar Sensors

Radar sensors have been used since World War II for the detection of surfaced or snorkeling submarines. Back then, submarines relied upon their batteries for submerged operations. Eventually their batteries would become drained to the point where they were forced to return to the surface and operate their diesel engines to re-charge the battery. While surfaced, the submarine was extremely vulnerable to detection by both radar and visual sensors. The addition of a snorkel enabled the submarine to operate its battery-charging diesel engines while minimizing its exposure to radar and visual sensors. Additionally, the background clutter of the surrounding ocean waves limited radar and visual detection. Also, the development of submarine-based electro-magnetic sensors provided the submarine commander with suffficient warning to dive if approaching radar emissions were detected.

Eventually, nuclear submarines where developed which eliminated the need to periodically recharge the batteries. Despite this significant advance, not all nations were able to build nuclear submarines due to financial and technological reasons. Those nations which remain committed to diesel power have pursued technology which limits the number of times the submarine has to recharge its batteries. However, many submarine commanders must still use their periscopes to provide final visual classification of targets prior to attack. Because of this requirement for target verification, radar systems are still used to detect submarine periscopes.

Today's airborne radar systems must be lightweight yet sufficiently capable for ASW operations, long-range detection and surveillance of surface vessels, airborne navigation, and weather avoidance. For that purpose, many Air ASW radar systems use different radar frequencies, scanning speeds, transmission characteristics, pulse lengths, and signal processing methods that reduce background sea clutter and enhance radar returns from exposed pericopes and submarine hulls. The hostile submarine using electro-magnetic sensors, however, can still detect ASW aircraft radar emissions at a much greater distance than the aircraft can detect the submarine by radar. Nevertheless, the threat of radar detection is sufficient to keep the submarine submerged. Radar systems now used aboard U.S. Navy ASW aircraft include the AN/APS-115 (P-3C), AN/APS-124 (SH-60B), and AN/APS-137 (S-3B, some P-3Cs).

Acoustic Sensors

Acoustic Sensors include those that use sound as a sensing medium. Doppler techniques allow the measurement of velocities. Ultrasound often provides more information about mechanical machinery vibrations, fluid leakage, and impending equipment faults than do other techniques. Sonar uses sound to determine distance using time-of-flight information. It is effective in media other than air, including

underwater. Caution should be used in that the propagation speed of acoustic signals depends on the medium. The speed of sound at sea level in a standard atmosphere is cs=340.294 m/s. Subterranean echoes from earthquakes and tremors can be used to glean information about the earth’s core as well as about the tremor event, but deconvolution techniques must be used to remove echo phenomena and to compensate for uncertain propagation speeds. membraneDrive electrodesDetector electrodesmembraneDrive

Explosive! New Sensor Technology

This type of ultra-sensitive sensors able to detect the presence of explosive materials. The sensors will have many security and military applications including being developed for use in the war against terrorism. It is the innovative collaboration of molecular biology and chemistry that has enabled the team to develop the novel sensor technology ‘nano-dog’ to be developed to commercial prototype.
Much as the glucose pens used by diabetics employ enzymes to test blood-sugar levels, this complex high-tech sensor uses uniquely adapted and patented enzymes to detect the presence of explosive materials.
Some bacteria contain enzymes which are able to chemically modify many of the commonly used explosives. These bacteria have been used, particularly in the USA, to clean up land contaminated by munitions. The enzymes within the bacteria convert the explosives molecules to less toxic products, cleaning the contamination in the process. In this new process some of these enzymes have been purified from the bacteria and subjected to genetic modification. This modification has enabled the enzymes to adhere to the surface of an electrode sensor, where they remain active. There, they can trigger an electrical signal when activated by the presence of minute amounts of explosives molecules.

Electronic Sensors

electronic sensor is a sensor that tells this information about itsenvironment by creating an electrical signal. This signal should change asthe thing it is measuring changes.

In your house you have a thermostat which controls the heat. It measuresthe temperature of the house, and converts this to an electrical signal.This signal is then sent down wires, back to the heater itself. When thesignal says its too cold, the heater comes on.There are many different things to measure heat, light, humidity, soundlevel, weight etc etc. each of these requires a different sensor. just howthis sensor converts say weight, to electricity, is a story of its own, andeach sensor has this physics. It can be simple or complicated. But in theend they convert their signals to something that can be sent down a wire, orsent over a radio wave etc etc

A sensor is something that tells something about its environment