Method and apparatus for eliminating aliasing

A system for reducing aliasing in a process control system comprising

• a process control module in the process control system that operates at a determined execution rate wherein the process control system comprises:
• field devices that provide analog output,
• an input/output device communicatively coupled with the field devices and a controller wherein the controller calculates a Nyquist frequency for the process control module based on the execution rate;
• an analog to digital convertor communicatively coupled with the input/output device;
• and
• a filter in communicatively coupled with the analog to digital convertor that attenuates a the frequency content if the measurement signal above the Nyquist frequency after the module signal is converted from analog form to digital form by the analog to digital convertor.

A computer system comprising a processor physically configured according to computer executable instructions for reducing aliasing in a process control system, a memory physically configured to store the computer executable instructions, an analog field device and an analog input/output device comprising an analog to digital convertor, the computer executable instructions comprising instructions for:

• setting a module execution rate for a module in the process control system;
• determining a Nyquist frequency for the module based on the module execution rate wherein the Nyquist frequency is two times the module execution rate;
• determining filtering to be applied after the analog to digital convertor based on the module execution rate;
• in the analog to digital convertor, setting the filtering applied after the analog to digital convertor based on the module execution rate;
• and
• attenuating a module signal at and above the Nyquist frequency for the module.