Data logger, oscilloscope, signal generator and more!

DrDAQ is a versatile instrument that connects to the USB port of any PC. Using the supplied PicoScope software it can be used as an oscilloscope, spectrum analyzer and signal generator.

From just £89.00


Measuring rainfall


Automating rainfall measurements

Rainfall is measured by catching water over a given time, in a suitable jar, usually with a Educational data loggerfunnel. 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. Neither is meant to be the definitive solution. I am sure that each could be improved upon, but they do both work.

rainfall method 1

rain_fall method 1 photo

rainfall method 2

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 10 mm. 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.


You may be able to think of other ways of doing the job. Perhaps changes in conductance of a wire dipping into the water as the level rises the more of the wire is immersed. Or you could devise an alternative method of your own. Whatever you do make sure you calibrate your signal.


Make a report describing how your system measures the level of water. You need to describe the design decisions, and the problems they were intended to overcome. You should provide calibration charts or graphs. Comment on the resolution of the devise, how small a change in level can it detect? Are there any sources of error — particularly systematic error? Your report could discuss alternative solutions, and their advantages and disadvantages.


  • I have been using my 4224 PicoScope for years. I travel abroad so this has been ideal due to its physical size. Storage of waveforms on my Laptop is very easy allowing me to quickly email waveforms to my Colleagues.

  • Not many USB scopes works on Win & Mac & Linux too, so that proves me that guys from Pico really cares about us, customers. This made my decision much easier when I was looking to buy an USB scope.

    Raul Trifan
  • We have been using Picoscope 6404D for quite some time, and are amazed by its accuracy and powerful emulations while working with numerous signal evaluations.

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  • PicoLog TC-08: This is a very nice unit that works consistently and reliably.

    Jeff Hulett
  • It is a great scope. I had a weird problem - it did not work on one of my PC’s. Customer service gave me first class service. If I could give 6 stars for customer service - I would do so.

    Niels Larsen
  • Perfect Partner for Development of Encoder controlled Stepper Motor Actuators. Since the included software is really stable, this type of device is a great tool for great tasks!

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  • A superb piece of equipment worth its weight in gold

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  • So simple to use & beats any other I have ever used hands down.

    John D Samsing
  • Great functionality in a compact size. I really like moving the mouse pointer to a position and having the Time and Voltage display the values at that point. Calibration equipment is a breeze with that feature.

    Don Horein

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