The Tmax method employs a temperature needle downstream (below) a line heater needle. The amount of time taken for the maximum rise in temperature following a heat pulse from the heater needle is recorded. According to well defined heat transport equations, derived from Marshall (1958), the heat velocity is calculated.
The SFM1 Sap Flow Meter can be configured to measure sap flow via the Tmax method. Raw temperature data is collected by the SFM1 instrument and later downloaded into the Sap Flow Tool software. In Sap Flow Tool, raw data can be quickly and easily manipulated to give heat velocity and sap flow data via the Tmax equations.