The PUM U-Pipe Pressure Gauge is said to be excellent for manometry in low pressure ranges. Construction of the device is the classical U-shaped glass tube, which is fixed on an aluminum retainer plate. The retainer plate bears a 2-mm graduated scale as well, which ensures the direct reading of the water column in mm when the tube is filled up with water. Connection to the device is through the 7 mm hose couplings at the two ends of the glass tube. The pressure difference at the two ends of the glass tube makes the liquid column in the tube move in either direction. The difference of the two ends of the liquid column can be read from the scale with 2 mm accuracy. The scale is formed in a way that it is not necessary for the liquid column to be at "0” when the device is in a no pressure state. When reading, the distance between the top and bottom liquid levels is indicated by two figures, which are to be added to receive the value referring to the total pressure. The manometer is available in 6 standard lengths, but customized options are possible. A datasheet is available at http://koboldusa.com/sites/default/files/product_files/pressure-gauge-U-pipe-PUM.pdf
Kobold Instruments Inc.