Test system controllers that feature peak detection software usually have Amplitude Control algorithms built into the software. The purpose of the Amplitude Controller is to control the maximum and minimum levels the test system applies to the specimen during the test. Since the Peak Detection software is already monitoring the peaks, the next logical step is to automatically alter the command drive signal so that the desired peaks are being met. Figure I shows what the system performance might look like without the Amplitude Controller engaged. Even though the system command signal is set up to run between two desired peak levels, the system is not able to achieve those peaks either due to the PID settings, system mechanical response or specimen response.
The Amplitude Control uses an iterative process whereby a small percentage of the difference between the desired and actual peak levels is added to the system command signal during each cycle until the desired peak levels are achieved. Figure II shows what the system command signal and actual response look like after the Amplitude Controller has done its job.
As long as the specimen and system response are somewhat linear, the Amplitude Controller is easy to set up so that your desired test levels are applied precisely throughout the test. In future test tips we will talk about how to set up the Amplitude Controller for test specimens and test systems that act linearly and non-linearly. At MDT we use all of the tools available to provide the most accurate test possible, and the Amplitude Controller is one of the more powerful ones.