scion xb speedometer is a device that measures the instantaneous speed of a land vehicle.Now universally fitted to motor vehicles, they started to be available as options in the 1900s, and as standard equipment from about 1910 onwards.Speedometer for other vehicles have specific names and use other means of sensing speed. For a boat, this is a pit log. For an aircraft, this is an airspeed indicator.he   speedometer was invented by the Croatian Josip Belušiæ in 1888, and was originally called a velocimeter speedometer xb.

Many modern xb speedometer are electronic. A rotation sensor xb usually mounted on the rear of the transmission, delivers a series of electronic pulses whose frequency corresponds to the rotational speed of the driveshaft. The sensor is typically a toothed metal disk positioned between a coil and a magnetic field sensor. As the disk turns, the teeth pass between the two, each time producing a pulse in the sensor as they affect the strength of the magnetic field it is measuring.

• A computer converts the pulses to a speed and displays this speed on an electronically-controlled, analog-style needle or a digital display. Pulse counts may also be used to increment the speedometer xb .

Another early form of xb electronic speedometer relies upon the interaction xb  between a precision watch mechanism and a mechanical pulsator driven by the car's wheel or transmission. The watch xb 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.The standards specify both the limits on accuracy and many of the details of how it should be measured during the approvals process, for example that the test measurements should be made (for most vehicles) at 40, 80 and 120 km/h, and at a particular ambient temperature. There are slight differences between the xb different standards, for example in the minimum accuracy of the equipment measuring the true speedometer xb of the vehicle.