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• Digital Power Meter

DashboardSpeedometers of a jeep A speedometer or a speed meter is a that measures and displays the instantaneous of a vehicle. Now universally fitted to, they started to be available as options in the 1900s, and as standard equipment from about 1910 onwards. Speedometers for other vehicles have specific names and use other means of sensing speed. For a boat, this is a.

Meter Reverse Check? Only difference was i wanted to knw how to reverse digital meter. N then IT connecter n u can change millege of ur car's meter.

For an aircraft, this is an. Is credited with creating an early type of a speedometer, which were usually fitted to. The electric speedometer was invented by the in 1888, and was originally called a velocimeter.

Contents. Operation Originally patented by Otto Schultze on October 7, 1902, it uses a rotating usually driven by gearing linked to the output of the vehicle's. The early Volkswagen Beetle and many motorcycles, however, use a cable driven from a front wheel. When the vehicle is in motion, a speedometer gear assembly turns a speedometer cable, which then turns the speedometer mechanism itself.

A small permanent magnet affixed to the speedometer cable interacts with a small aluminum cup (called a speedcup) attached to the shaft of the pointer on the analogue speedometer instrument. As the magnet rotates near the cup, the changing magnetic field produces eddy currents in the cup, which themselves produce another magnetic field. The effect is that the magnet exerts a on the cup, 'dragging' it, and thus the speedometer pointer, in the direction of its rotation with no mechanical connection between them. The pointer shaft is held toward zero by a fine.

The torque on the cup increases with the speed of rotation of the magnet. Thus an increase in the speed of the car will twist the cup and speedometer pointer against the spring. The cup and pointer will turn until the torque of the eddy currents on the cup is balanced by the opposing torque of the spring, and then stop. Given the torque on the cup is proportional to the car's speed, and the spring's deflection is proportional to the torque, the angle of the pointer is also proportional to the speed, so that equally spaced markers on the dial can be used for gaps in speed. At a given speed the pointer will remain motionless and pointing to the appropriate number on the speedometer's dial.

The return spring is such that a given revolution speed of the cable corresponds to a specific speed indication on the speedometer. This calibration must take into account several factors, including ratios of the tailshaft gears that drive the flexible cable, the final drive ratio in the, and the diameter of the driven.

One of the key disadvantages of the eddy current speedometer is that it cannot show the vehicle speed when running in reverse gear since the cup would turn in the opposite direction - in this scenario the needle would be driven against its mechanical stop pin on the zero position. Electronic.

See also: Many modern speedometers are. In designs derived from earlier eddy-current models, a rotation sensor mounted in the transmission delivers a series of electronic pulses whose frequency corresponds to the (average) rotational speed of the, and therefore the vehicle's speed, assuming the wheels have full traction. The sensor is typically a set of one or more magnets mounted on the output shaft or (in transaxles) differential crownwheel, or a toothed metal disk positioned between a magnet and a. As the part in question turns, the magnets or teeth pass beneath the sensor, each time producing a pulse in the sensor as they affect the strength of the magnetic field it is measuring. Alternatively, in more recent designs, some manufactures rely on pulses coming from the ABS wheel sensors. Most modern electronic speedometers have the additional ability over the eddy current type to show the vehicle speed when moving in reverse gear.

A computer converts the pulses to a speed and displays this speed on an electronically controlled, analog-style needle or a. Pulse information is also used for a variety of other purposes by the or full-vehicle control system, e.g. Triggering ABS or traction control, calculating average trip speed, or to increment the in place of it being turned directly by the speedometer cable. Another early form of electronic speedometer relies upon the interaction between a precision watch mechanism and a mechanical pulsator driven by the car's wheel or transmission. The watch mechanism endeavors to push the speedometer pointer toward zero, while the vehicle-driven pulsator tries to push it toward infinity.

The position of the speedometer pointer reflects the relative magnitudes of the outputs of the two mechanisms. Bicycle speedometers. A speedometer showing mph and km/h along with an odometer and a separate 'trip' odometer (both showing distance traveled in miles).

The amended Road Vehicles (Construction and Use) Regulations 1986 permits the use of speedometers that meet either the requirements of EC Council Directive 75/443 (as amended by Directive 97/39) or UNECE Regulation 39. The Motor Vehicles (Approval) Regulations 2001 permits single vehicles to be approved. As with the UNECE regulation and the EC Directives, the speedometer must never show an indicated speed less than the actual speed.

Digital Power Meter

However it differs slightly from them in specifying that for all actual speeds between 25 mph and 70 mph (or the vehicles' maximum speed if it is lower than this), the indicated speed must not exceed 110% of the actual speed, plus 6.25 mph. For example, if the vehicle is actually travelling at 50 mph, the speedometer must not show more than 61.25 mph or less than 50 mph. United States Federal standards in the allow a maximum 5 mph error at a speed of 50 mph on speedometer readings for commercial vehicles. Aftermarket modifications, such as different tire and wheel sizes or different differential gearing, can cause speedometer inaccuracy. Main article: devices are positional speedometers, based on how far the receiver has moved since the last measurement.

Its speed calculations are not subject to the same sources of error as the vehicle's speedometer (wheel size, transmission/drive ratios). Instead, the GPS's positional accuracy, and therefore the accuracy of its calculated speed, is dependent on the satellite signal quality at the time. Speed calculations will be more accurate at higher speeds, when the ratio of positional error to positional change is lower. The GPS software may also use a calculation to reduce error. Some GPS devices do not take into account the vertical position of the car so will under report the speed by the road's gradient. As mentioned in the article, GPS data has been used to overturn a speeding ticket; the GPS logs showed the defendant traveling below the speed limit when they were ticketed. That the data came from a GPS device was likely less important than the fact that it was logged; logs from the vehicle's speedometer could likely have been used instead, had they existed.

See also. References. ^ Harris, William (10 July 2007). How stuff works. Retrieved 30 January 2015. Retrieved 30 January 2015.

Retrieved 30 January 2015. Sobey, Ed (2009). Chicago Review Press. Retrieved 30 January 2015. 26 April 2005. Retrieved 30 January 2015.

UN Economic Commission for Europe. Retrieved 30 January 2015. European Commission. Retrieved 2017-04-08. European Commission. Retrieved 2007-01-07. European Commission.

Retrieved 2007-01-07. Road Vehicle Certification System. Retrieved 2008-01-07. Commonwealth of Australia Law. Retrieved 2008-01-14.

Leslie Felix (2004). National Motorists Association Australia. Retrieved 2008-01-14. Victoria Road Safety Committee, Inquiry Into the Demerit Points Scheme. November 1994. Retrieved 2008-01-14. Written Answers, Hansard (UK Parliament proceedings) Monday, 12th March 2001.

Retrieved 2008-01-07. Office of Public Sector Information. Retrieved 2007-12-19. Retrieved 30 January 2015. External links has media related to.