Method and apparatus for eliminating aliasing
First Claim
1. A method of reducing aliasing in a process control system wherein the process control system comprises at least one analog device and an analog to digital convertor, the method comprising:
- 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;
determining a filtering after the analog to digital convertor based on the module execution rate;
in the filter after the analog to digital convertor, setting the data sampling rate in the analog to digital convertor based on the module execution rate; and
attenuating a frequency content of the measurement signal at and above the Nyquist frequency for the module.
1 Assignment
0 Petitions
Accused Products
Abstract
In order to reduce or eliminate aliasing in a process control network, filtering of a measurement signal may be set based on the module execution rate in a process control system. A Nyquist frequency for the module may be determined based on the module execution rate where the Nyquist frequency may be twice the execution rate. Filtering after an analog to digital convertor may be set based on the module execution rate. In the analog to digital convertor, digital filtering after the converter may be set based on the module execution rate and the frequency content of the analog signal may be attenuated by a filter at and above the Nyquist frequency for the module execution rate.
-
Citations
20 Claims
-
1. A method of reducing aliasing in a process control system wherein the process control system comprises at least one analog device and an analog to digital convertor, the method comprising:
-
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; determining a filtering after the analog to digital convertor based on the module execution rate; in the filter after the analog to digital convertor, setting the data sampling rate in the analog to digital convertor based on the module execution rate; and attenuating a frequency content of the measurement signal at and above the Nyquist frequency for the module. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. 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. - View Dependent Claims (12, 13, 14, 15, 16, 17)
-
-
18. 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. - View Dependent Claims (19, 20)
-
Specification