Dynamax HPFM3, Installation And Operation Manual, Page: 59 / 86

Revision: JUNE 2017 59
Figure 12
Comparison of transients measured on most sensitive range (Green range)
Flow was into a 1.5 m length of tubing connecting the 8WO to the smallest compression fitting connected to a solid plug
1.5 mm OD. For the graph on the left a 1.5 mm OD plastic tube was used on the right a 3 mm OD plastic tube. The higher
plateau on the right is due to the higher elasticity of the larger tube. The slight slope on the plateaus may be due to minor
leaks in the 8WO and the compression fittings or it might be due to non-linear elastic effects. Clearly the 1.5 mm tube is
preferable for measurements of conductance of an unknown and the slight slope on the plateau should be subtracted from
any conductance calculated on an unknown.
8.4 Air Bubbles
Air bubbles in the compression fitting or base of stem will influence the accuracy of conductance measurements, but cannot
always be eliminated. Air bubbles are sometimes present in the stems or roots of plants and often cannot be eliminated.
Generally, air bubbles can be eliminated from the HPFM. Figure 13 & 14 show some typical transients with the influence
of air bubbles.