Response of the SFA to  the various active actuation modes. A) Mode 1 actuation (vacuum @ -90 kPa  followed by passive decompression) showing a slower response during relaxation  phase with some unstable zones while recovering. B) Mode 2 actuation (vacuum @  -90 kPa followed by active decompression using 10 kPa) showing a response that  is five times faster and more stable. Plots are an average over 20 cycles. Mode  2 is faster and more accurate than mode 1 which is five times slower with some  instability during the relaxation phase.