16 Facts About Incremental encoder

An incremental encoder is a linear or rotary electromechanical device that has two output signals, A and B, which issue pulses when the device is moved.

An incremental encoder employs a quadrature encoder to generate its A and B output signals.

Resolution of an incremental encoder is a measure of the precision of the position information it produces.

The incremental encoder is mechanically attached to the device to be monitored so that its output signals will change as the device moves.

In commercial marine radar antennas, a rotary incremental encoder is typically attached to the rotating antenna shaft to monitor the antenna angle.

For example, in the case of a linear incremental encoder that produces 8000 counts per millimeter of travel, the position in millimeters is calculated as follows:.

In such cases, the mechanical system is homed by moving it until the Incremental encoder interface receives the sensor signal, whereupon the corresponding position value is jammed into the position counter.

Incremental encoder interfaces are primarily concerned with tracking mechanical displacement and usually do not directly measure speed.

For example, in the case of a rotary incremental encoder that produces 4096 counts per revolution, which is being read once per second, the software would compute RPM as follows:.

An incremental encoder interface is an electronic circuit that receives signals from an incremental encoder, processes the signals to produce absolute position and other information, and makes the resulting information available to external circuitry.

Incremental encoder interfaces are implemented in a variety of ways, including as ASICs, as IP blocks within FPGAs, as dedicated peripheral interfaces in microcontrollers and, when high count rates are not required, as polled GPIOs.

However, the incoming Incremental encoder signals are asynchronous with respect to the interface clock because their timing is determined solely by Incremental encoder movement.

When only A or B changes state, it is assumed that the Incremental encoder has moved one increment of its measurement resolution and, accordingly, the quadrature decoder will assert its count enable output to allow the counts to change.

When neither A nor B changes, it is assumed that the Incremental encoder has not moved and so the quadrature decoder negates its count enable output, thereby causing the counts to remain unchanged.

In many Incremental encoder applications this is a catastrophic event because the counter no longer provides an accurate indication of Incremental encoder position.

From an application's perspective, the fundamental purpose of an incremental encoder interface is to report position information on demand.