Commissioning of the HEPI Pump servo continues at LHO with the tweaking of PID control loop parameters.  Spectra of the voltage output from the Honeywell Pressure sensors are attached below.  The maximum allowed pump pressure fluctuations in PSI/sqrt(HZ) are calculated in the document T1100198.  The data was taken from the pressure sensor transducer outputs in-line with the servo box.  Data was then converted from Volts to PSI per the manufacturer's specifications (3000PSI/1V) .  A Dataq Instruments interface was used to record voltage input and record data in a text file using its software on a laptop separate from the single board computer in the servo box.  

The first plot is with no PID servo enabled; it is simply with the motor controller set at a speed that read out ~80 PSI.  The subsequent plots have PID parameters listed in title of the plot.  The maximum allowed PSI fluctuations curve calculated from the above-mentioned paper is plotted as well.  So far, the conservative PID gains have not brought the performance to the maximum allowed fluctuations.  The spectra does decrease in magnitude over all frequencies with increasing PID gains. Next, more aggressive PID gains will be implemented (several 10s to 100s) and data collected.  Also of note, new accumulators were installed Monday and pressurised to 75 PSI.