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Speed Measuring Instruments

Updated on January 21, 2017
Odometers and speedometers are two of the many instruments used to measure speed.
Odometers and speedometers are two of the many instruments used to measure speed. | Source

Speed measuring instruments vary with the job. Whether measuring traveling speed, wind speed, acceleration or engine speed, there is a proper instrument for calculating that form of speed. Police use RADAR and LIDAR to measure traffic speed. Cars have speedometers for travel speed and tachometers for engine speed. Accelerometers are also used with car speed measurements. Meteorologists use anemometers and radar to create their weather forecasts.

Tachometers for Engine Speed

Tachometers measure the engine speed in revolutions per minute (rpm). This instrument determines the rotational speed (how fast it's spinning) of a shaft or disk in the engine and displays the reading on a calibrated analog dial display on the dashboard of a car, aircraft or other vehicle. The display indicates a safe rpm range, which is meant to help the driver determine the best gear and throttle settings, and correct traveling speeds. Extended periods of high speed travel, with excessive engine speeds, can lead to insufficient lubrication, an overheated engine because the cooling system can't keep up, and wear-and-tear on engine parts from going beyond their speed capacity.

The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...

Speedometers for Travelling Speed

Speedometers measure the traveling speed of land vehicles. They are used to help drivers determine their driving speed and maintain it at save and realistic levels. These meters use magnets and a set of rotating cables connected to the transmission to determine the rate of travel, which is shown on an analog display on the vehicle's dashboard. US federal standards allow for a 5 mile per hour (mph) manufacturer variations in speedometer readings for traveling speeds around 50 mph. tire changes, wheel changes, gear differential adjustments can also affect speedometer accuracy.

Accelerometers for Measuring Acceleration and Deceleration

Accelerometers measure the rates of acceleration and deceleration of a vehicle to determine whether the drive train and braking systems are functioning correctly. This instrument has been used to show a vehicle's engine power by demonstrating how fast that car or truck can get from 0 to 60 mph. They can also be used to follow animals at a distance.

RADAR for Determining Vehicle Speed

Police use radar to check for speeders. Radar uses the Doppler effect, which bounces sound waves off moving vehicles, then calculates the sound wave frequency as the return to the instrument. Soundwave frequency increases the closer the vehicle is to the instrument, and decreases as the distance between the vehicle and radar gun get wider. The car or truck speed is calculated by determining how long or short the Doppler Effect is. If the Doppler Effect is spread out it indicates a slower speed, but when bunched close together, it indicates a faster speed.

Meteorologists use RADAR to track the movement of weather systems. Not only can they calculate how fast the storm is moving, but also in which direction it travels, all based on the Doppler Effect.

LIDAR for Determining Vehicle Speed

LIDAR stands for Light Detection and Ranging. Police use LIDAR to calculate car and truck speed much like RADAR is used, only LIDAR uses light instead of sound. LIDAR aims an infrared light beam toward a vehicle and measures how long it takes for the light waves to reflect back. The light pulses have the advantage of traveling at the speed of light instead of the speed of sound, which provide a reading a bit more quickly than RADAR.

Average Speed Computers 81

Another weapon in the police arsenal is the average speed computer. Airplanes and a stopwatch are used to time how long it takes a vehicle to get from a starting point to an end point marked out on the street pavement below. An on-board computer calculates the speed using an average speed program. If the vehicle appears to be speeding, the pilot radios ahead to a police patrol unit, who then can stop the driver and give him or her the gift of a speeding ticket.

Anemometer 46

Anemometers are wind speed instruments used by meteorologists. These devices have 3 or 4 cups attached to a central spoke. As the cups catch the movement of air, they spin on the spoke, and the revolutions per minute are converted to an air speed or wind speed.

No matter what is being measured for speed, having the right instrument is essential. It is also important to Make sure that instrument is working properly in order to obtain correct speed measurements.

© 2011 Joan Whetzel


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      shiv mittal 6 weeks ago

      introductory information,pls give detailed information, working,construction,various applications of various methods of speed measurements.

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      shiv mittal 7 weeks ago

      nice introduction of speed measurement