4-20mA Absolute Encoders
The 4-20mA analog output absolute encoder is one of easiest to understand.
Many absolute encoders provide their position information via a communications fieldbus protocol, such as Ethernet I/P, CanOpen, EtherCAT, Profibus etc, to the control or display system.
In order to test, check, or fault find such a fieldbus system you need special programming tools and access to the programming environment. This usually entails a laptop, some special software, cables, and some training.
The advantage of a 4-20mA analog signal from the encoder, means that anyone with a multi-meter can quickly check the status of the encoder signal information.
Another advantage of a 4-20mA signal is that it is relatively noise (electrical) immune, and is suitable to run over longer distances, even a few hundred meters.
Communications protocols sometimes attract a royalty charge from the developers making them more expensive; whereas a 4-20mA signal is as royalty free as the sunshine.
The one down side is that an analog input on a PLC is not cheap, and you need as many analog channels as device signals on the project. Whereas a single communications port can accept inputs from multiple encoders.
POSITAL FRABA offer a wide range of encoders with a 4-20mA output. The more cost effective and common single turn encoder is by default 0 ~ 360° = 4-20mA, and since these are programmable encoders, PCA can easily reconfigure these locally to any angle range in between.
Multiturn encoders are also available for up to 16 revolutions or 5760°
Aside from the 4-20mA analog standard, POSITAL also offer encoders with a 0-10V signal, or even 0-5V signal output option.
Another feature with POSITAL’s 4-20mA analog encoders, is that the direction the signal travels in can be reversed by simply applying the supply voltage to one of the pins. Similarly there is a zero° pin, which allows you to set the home position, or top-dead-centre (TDC) position, so that it becomes the 4mA position.
For further information on PCA's range of 4-20mA absolute encoders please call 02 9482 3733. A member of our expert team will gladly answer any questions that you may have.