Frequency response Tests

[ILC_HParticipant Karma: 15Rank: Padawan]

Hi everyone,
So i have a closed loop System, wich consist of a pump and Servomotor controlled with PID-Controller by an Allen-Bradley’s PLC (ControlLogix5561). I need to perform frequency Response Tests on the System in order to obtain the bode Plot (Gain and Phase over Frequency) of the system.
This means i need to generate sine wave at differents frequencies to excit the Systems. The Response of this Input will help me to generate the Bode plot.

I am used to Programms application with PLC (specially Siemens s7 1500, I am new to allen Bradley) but i have never have to generate sine wave.
So my Question is, it is possible to performs such Tests with a PLC only or do i Need an extra Signal Generator?

[Fred GrahamKeymaster]

Hi there and welcome to the forums! Ah yes good old Bode, very useful to identify stability. A little off topic with what you’re trying to do, however, I did do a video where I created a “function generator” per say to generate a sine wave that is used DDE/OPC to populate an Excel spreadsheet in real-time from a logix controller. You can have a look at the video here:

[ILC_HParticipant Karma: 15Rank: Padawan]

Hi Fred , thanks for this Video, very useful and informative, although it doesn’t answer my Question. I will definetly need to configure an OPC communication for my Project.
The sine Generator is cool but can someone use it for frequency test? I mean is the PLC robust enough to generate high frequency sine wave ? (i.e Min. 500hz ).

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