Absolute Encoders

Absolute rotary encoders provide an upper-level controller with information that precisely describes the position of the encoder shaft at any moment in time.  

The shaft position can be between measured between 0 to 360 degrees on a single turn absolute encoder, and in multiple of turns of 360 degrees, up to 1000’s of degrees, on a multiturn absolute encoder.  

There is always a start and an end point, and the output signal information represents exactly where the shaft position is in relation to these points.  

Once the end point of an absolute encoder is reached, the signal starts at the zero point again, so this must be considered when selecting an absolute encoder and designing the control program. 

Unlike incremental encoders, the absolute encoder reader or upper-level controller is not required to calculate and remember the encoder position, as the absolute encoder takes care of this. 

Absolute encoders
Absolute encoders

 

Single Turn Absolute Encoders 

Single-turn encoders provide a measurement range of 360 degrees (one turn). 

Multiturn Absolute Encoders 

Multiturn encoders provide a measurement range of more than 360 degrees by additionally measuring the number of revolutions. 

Advantages of Absolute Encoders 

One key advantage of absolute encoders is that they provide exact position information at any time even after power up. This means that the upper-level controller does not have to perform a “Home” routine, or a reference run, which is the case when incremental encoders are used.  

This means greater safety and more efficiency of the machines and processes. 

Absolute Encoder Signals 

An absolute encoder signal is commonly an industrial communication protocol such as: CANopen, Profibus, DeviceNet, J1939, Interbus, EtherCAT, Ethernet/IP, ProfiNet, Powerlink, Modbus RTU and Ethernet TCP, or SSI. 

CANopen Absolute Encoder
CANopen Absolute Encoder
EtherCAT Absolute Encoder
EtherCAT Absolute Encoder
IO-Link Absolute Encoder
IO-Link Absolute Encoder

 

It is also possible for the absolute encoder signal to be an analog control signal, such as: 0-20mA, 4-20mA, 0-10V, 0-5V. 

What is special about POSITAL Absolute Encoders? 

To remember the positional information without power being connected, many other absolute encoders have an elaborate arrangement of mechanical gears to record multiples of turns, and they often have batteries that may leak or need changing. 

Mechanical gears make encoders physically large, and are complicated to manufacture, and they are more susceptible to failure. 

POSITAL pioneered the Wiegand Technology in encoders, which is used in all their IXARC magnetic absolute encoder. This means is no gears, so there are fewer mechanical parts to fail. Plus, no battery backup is necessary, you never have to change batteries and there is no risk of damage being caused by a leaking battery. 

Even though POSITAL still manufacture absolute encoders with optical and mechanical technology, the new generation magnetic absolute encoders are more cost effective and reliable. 

Absolute encoders have typically been physically large. POSITAL now offers compact size absolute encoders down to 36 mm Ø. 

POSITAL absolute encoders also have unique feature options such as stainless-steel bodies, IECEx and SIL safety approvals, and high shock and vibration resistance. 

Absolute Encoder Applications 

Since absolute encoders can connect to the most common industrial PLC’s and controllers in the world, they are often used in applications such as: factory automation, water treatment, oil and gas industries, wind turbines, solar plants, healthcare equipment, and mobile moving machines. 

Absolute encoder application - industrial automation
Absolute encoder application - industrial automation