There is no change in pressure as I move the plunger. Is the VPM leaking?

Complete the following pressure leak test:

1. Make sure the tubes have been inserted fully and the knurled nuts tightened.   
                  
            
2. Check the fluid cell is not causing the leak, e.g. hold finger tightly over the fluid cell port of the airline and apply a pressure to separate a potential leak from an incorrectly seated fluid cell nozzle or o-ring. 
3. Check that the vent valve closes smoothly over the sealing surface without any sticking or squeaking. 
4. Set up a system with a nanopore and let the system run for a few minutes at two pressures. Use the Classic Capture mode to record this test. Suggested conditions:
   • Nanopore: NP250/NP300
   • Particles: CPC200 (1:200) or CPC400 (1:500). Aim to have a blockade magnitude of 0.3 nA. 
   • Electrolyte: PBS + 0.03% surfactant
   • Applied pressures: e.g. 2 and 10 mbar

The blockade rates at both pressures should remain constant and the higher pressure measurement should have a significantly larger rate.