The pressure cell and flow pump must be calibrated against a standard.
The probe itself must be demonstrated to be pressure tight. This is done before field work starts by capping off the lower end of the instrument then operating the full permeameter system as if it were a real test.
A successful demonstration would show that even at the lowest flow rates of which the system is capable the internal pressure continues to rise - a leakage path shows itself as an apparent steady state.
There is considerable interest in measuring the engineering properties of waste. Cambridge Insitu have used a self boring pressuremeter (shown in Figure 1) to make in situ tests in and around domestic waste sites.
