Feedback types

Types of feedback

Incremental encoders

Incremental encoders provide digital pulses or counts back to a PLC or VFD. A PLC can be programmed to use encoder pulses to synchronize, position, or vary the speed of an electric motor. Incremental encoders can be mounted on limit switches, reducers, or electric motors. Incremental encoders offer a variety of different pulses per revolution (PPR). Incremental encoders can provide as little one pulse per revolution up to several thousand pulses per revolution.

Absolute encoders

Absolute encoders work similarly to incremental encoders. Pulses or counts are monitored by a PLC or VFD. Ethernet/IP encoders communicate with a PLC over an Ethernet cable. Unlike incremental encoders, absolute encoders do not lose position or counts when power is cycled. There is no need to reference or home absolute encoders after a power cycle.

Potentiometers

Potentiometers provide a 0 – 10 VDC analog output signal. This analog signal can be used by a PLC to scale the position of a device. Potentiometer feedback can be found in rotary or string type devices. Rotary potentiometers can be mounted on limit switches. String type potentiometers are usually mounted to equipment. Potentiometers are useful when an extremely precise degree of accuracy is not needed.

Linear Sensors

Linear sensors output a 0 – 10 VDC, or 4 – 20mA analog output signal. Like a potentiometer this analog signal can be used by a PLC to scale and position or control an electric motor. Depending on the location of the linear sensor in an application, linear sensors provide the highest degree of accuracy. Linear sensors come in a variety of configurations. Rod, magnetic, and non-contact sensors are most frequently used.

Load Cells

Load cells are feedback devices that detect load. Load cells can detect load in tension, compression, or both tension and compression. Load cells are ideal for applications where load detection or load processes are needed. Load cells like linear sensors come in a variety of configurations such as pancake, donut, or pin style.