[Insert Fig. 1 here]
2.1.3 Principles of the Double-Ratio Method (DRM)
To alleviate the negative bias of the HRM at high V , we propose a
new method, the DRM, that uses a three-step approach to estimateV . First, V 12 is estimated as in the HRM.
Second, an additional estimate of sap velocity
(V 23, Eqn. 6 ) is computed using the
temperature rises at Probe #2 and #3, where Probe #3 is located
distal to Probe #2 at the same distance as Probe #2 is from Probe #1
(so x 3 = 3ยทx 2):