Using Absolute Encoders or Resolvers With NI Products

Issue Details

Is it possible to use an absolute encoder or resolver with NI products?  Is using an absolute encoder the same as using a quadrature encoder with a counter?
 

Solution

Yes, it is possible to use an absolute encoder with NI products however it is not done in the same way as a quadrature encoder.  More precisely, it is not possible to use an absolute encoder or resolver with a counter.  

An absolute encoder will have multiple data wires coming out of it that represent the absolute position of the encoder.  For example, a 12 bit absolute encoder will have 12 data wires that will output 12 digital signals representing the position in a 12 bit binary number.  If you place these in sequential order and the typecast this binary number to a 12 bit numerical value you can directly get the position of the encoder.  

It is therefore possible to use a NI DIO board that has 12 or more DI lines (for a 12 bit encoder) to acquire the current absolute position of the encoder.  To do this, wire the 12 digital data lines to the 12 digital input lines and sample periodically these lines to get the 12 bit binary representation of the position.  Once this is acquired into LabVIEW, simply convert this 12 bit number into a numeric representation of the number to get the position.