The Pump Servo commissioning at LHO continues.  A lead was placed inside the servo box on the circuit board at TP7, which is after the gain and is the signal the DAQ receives.

The leads were then plugged into an SR785 and an oscilloscope to monitor voltage signal and to take an amplitude spectrum of the signal with and without PID control.

Spectra were taken from the pressure sensors #1 and #4.  Sensor #1 being before the fluid reaches the accumulators and #4 being after the final accumulator. Sensor #4 monitors the pressure as it leaves the pump station.  Data was also taken of the pressure sensor outputs without pressure in the system as a baseline noise measurement of the sensors. 

The first plot is of Sensor #1 and has the PID ON/OFF and sensor noise traces on it. The second plot is of Sensor #4.

The data taken with Sensor #1 has some double resonance peaks at about 10, 20, and 30Hz while the data from Sensor #4 shows these resonances as a single peak at the same frequencies.  Sensor #1 also has a peak at 5Hz that is not present in the data from Sensor #4.  The data also shows little to no improvement in the PSI fluctuations with the PID control ON or OFF.  However, these PID parameters were very conservative with the parameters of P=2, I=1, and D=0.1.  

The sensor noise is also very close to the fluctuation with and with PID control for frequencies above 2Hz.  It looks like the limit on controlling the pressure is the fluctuation of the sensor readout itself.  However, the pressure fluctuations are below the pump servo goal, except for the 10, 20, and 30 resonance peaks present on all the traces.