Super accurate level meter

Step 2 Measuring limits

Before making a measurement lay down the ruler until water runs out the hole at the top of the tubing at the top of the ruler, and there are no air bubbles left in the line. This will ensure an accurate reading.
Next place the reservoir at your reference point. This point is normally going to fall between the highest and lowest points that would be possible during the extent of your measuring. This should fall between the highest and lowest points of your water level on your reservoir. On this example I have over 9 inches of reservoir height to play with.