A suspension assembly for an agricultural machine, adapted to reduce bump steering. The heat exchanger tube comprises a tube body, in which a plurality of lobes are formed on an outside surface of the tube body around the peripheral of the tube body and a plurality of ribs are formed on an outside surface of the tube body along the length of the tube body. Therefore, the device has a configuration wherein the reception fibers 12, 13 receive two kinds of respective light beams with different solid angle distributions, whereby the device can also obtain angular information, in addition to intensity information of light emerging from a measuring object 100.