Sap flow sensors are widely used to quantify whole plant water use, responses to environmental conditions and modeling transpiration rates. Sap flow sensors are instruments that measure the movement of water through a tree’s xylem, however the installation of sap flow sensors requires a probe insertion that triggers physiological responses that can affect sap flow measurements. This wounding response must be accounted for when generating whole plant rates of transpiration. The time it takes for wounding tissue to develop and stabilize may differ among sap flow sensors, I will compare three sensors, the ICT, JS5 and the RSF. I ask the question 1) How does commercially available sensor (ICT) compare to the DIY version of the sensor (JS5)? 2) How do different sap flow sensor systems vary in the wound response they induce? I hypothesized that H1: The JS5 and ICT sensors provide comparable values despite small differences in probe design and datalogger configuration.?H2: The ICT and JS5 will have a similar wound response (both in timing and magnitude of impact on heat pulse velocity), compared to the RSF probe. I will install all three sap flow sensors into one red oak and one red maple tree, and during that time I will collect data from each sensor, assess internal wounding by injecting dye below each probe site and then taking a core sample above the wound. The core will be examined to see how the dye moved through the xylem and that will allow me to detect whether any vascular connections were disrupted. I will compare sensor data, and dye movement between the oak and maple to evaluate how sensor design and species influence wounding. By comparing the performance of two low cost, DIY sensors (the JS5 and RSF) with a more established commercial system (ICT), this project evaluates whether inexpensive alternatives can provide reliable sap flow measurements.