Single-arm water manometer (30/11/11)

Most manometers are of the U-tube variety. It's possible to replace one arm of the U-tube with a resevoir, so long as it has a much larger diameter than the remaining tube. Here, I'm using a jam jar as the resevoir, with pipe connections soldered to the lid. The main column is a piece of 5mm bore PVC tubing stretched between two brass fittings which are screwed to a long piece of wood. A measuring tape is used as a scale. The PVC tubing isn't ideal, since it's a bit narrow and water has a tendency to stick to it.

Click here for a PDF of the layout and instructions for use.

It can measure positive and negative pressures, depending on where the unknown pressure is connected to. The maximum pressure readable is about 2m of water (limited by the height of the garage roof!), which corresponds to about 150 Torr.

Top and bottom connectors for main column

Mockup of how the tubing is connected

Top of column with scale in place

Bottom of column

Connectors are soldered to lid of jam jar

Jam jar used as resevoir