Disclosed herein is a sensor unit that is positioned at a location in a conduit for measuring a property of a fluid flowing through the conduit, the sensor unit comprises: a sensor support; a body section including proximal and distal sides and a center having a chamber, the chamber having a lower part and a top part with the lower part providing an open path between the proximal and distal sides of the body section, providing a flow channel through the body section; a socket in the top part of the chamber, the socket configured to receive the sensor support; a gasket located on top of the sensor support; e) a clamp configured to compress and hold the gasket and sensor support in place in the socket; and at least one sensor configured to measure a property of the fluid; wherein the sensor support maintains the at least one sensor in position relative to the walls of the flow channel through the sensor unit and at a constant depth relative to the fluid flowing through the sensor unit.