A field use optical grain characterising system (101) includes a generally rectangular prismatic composite body (102) that defines a component cavity (103). A substantially vertical elongate channel (104) extends within cavity (103) for housing a grain sample (not shown). An electromagnetic radiation source, in the form of a 12 Volt halogen lamp (105), is disposed within cavity (103.) for directing NIR light into channel (104). An optical detection system (107) is disposed within cavity (103) for sensing selected light emerging from channel (104) and for providing a sensor signal. A processor, which is included within detection system (107), is also disposed within cavity (103) and is responsive to the sensor signal for providing data indicative of a characteristic parameter of the grain sample. A display device, in the form of a 5.7-inch touch screen LCD display (108), is connected with body (102) for selectively presenting the data.