New type of manometer was deviced for the purpose of measuring small difference in pressure accurately. This manometer is placed on the balance pan, and the head difference Δh can be obtained by weight difference of liquid in manometer (Δh=ω/ρgA), in place of direct reading of Δh on manometer. These devices was used in combination with pitot-static tube, and mean velocity plofile near the rough wall in sheet flow become clear. In this paper, the authors report the outlines of these devices, method of calibration, method of measurement, and showed a fews results of measurement. According to these results, we evaluate the effect of surface tension which is the largest cause for the error in these experiment.