How To Measure Rainfall

Rainfall is measured by catching water over a given time, in a suitable jar, usually with a funnel. The tedious part is going out and measuring the amount of water everyday. The task is to devise a way of monitoring the level of rainwater continuously without the need to go outside. # You will need DrDAQ data logger connected to a PC # 50K linear potentiometer # A good sized beaker or measuring cylinder # A stand, boss and clamp # Materials to make lever arm and float The investigation In industry there are a significant number of situations where the height or depth of a liquid is required. The most common everyday use is in the petrol tank of a car or even the cistern in a flush toilet or water tank. One way to monitor the level of liquid in a container is to use a float, which rises and falls with the level of the liquid. Then the movement of the float needs to be converted into an electrical signal. One way to do this is to make the movement of the float turn the spindle of a rotary potentiometer. Some suggestions Below are two methods by which the spindle of a rotary potentiometer can be used to detect movement of a float. Niether is meant to be the definitive solution. I am sure that each could be improved upon, however they do both work. Having decided on how you are going to get the float to rotate the potentiometer spindle you then simply connect the potentiometer to the resistance and ground terminals on the DrDAQ datalogger.Turn your PC on and run the Picolog software setting it to monitor resistance over say 48 hours with a sample every 15 minutes. Note however that you will have to do some calibration so that changes in resistance monitored by the DrDAQ can be converted into millimetres of movement of the float. For example say that a 1k increase in resistance is equivalent to the float rising by 10mm. Then by selecting the parameter setting in the Picolog software we can multiply our resistance by 10 to give us our depth of rainfall. This new data "mm of rainfall" can now be displayed in the form of a graph with axes correctly labelled.