Penetrometer

1.8 billion people around the world don’t have access to safe water and 2.4 billion lack access to adequate sanitation. Women and children spend more than 4 hours walking for water each day, and more than 840,000 people die each year from water-related diseases.

Water For People is an international non-profit working across 9 countries to bring safe water and sanitation to 4 million people. Water for People want to see communities break free from the cycle of poverty and spend time growing, learning, and thriving, instead of walking for water and fighting off illness.

Water for People have been installing pit latrines in various different areas in Africa and South Asia. To measure how well the pit latrines are working,  a “Penetrometer” was designed as part of a research project. This prototype worked well, but more were needed and the unit needed to be more robust, easier to use and easier to repeat.

Solution

We helped to develop the electrical design and control system for the second version of the penetrometer.

The unit is a controlled rod which pushes from the top down into the pit latrine sludge. The rate of movement and the force on the rod are measured and recorded, along with location and time data. This gives information into the ‘health’ and capacity of the latrine.

We produced a full electrical design and worked to find robust and reliable components which were also lower cost by using as much off-the-shelf equipment as possible.

The data logging is performed using a LabJack U6 data-logger and control unit. This unit worked, along with a bespoke program written for DAQFactory, to control the system and take data files.

The unit is all powered from a 12V lead acid battery with charging facility. There are limit switches and an emergency stop to for safe use of the unit. We needed to keep the full weight under 20kgs so it can be moved to different sites and to places where there are not good roads.

Force data is taken from a load cell and distance is measured by counting pulses from an encoder on the motor.

Three of these units were built for various projects. Initially testing will be performed to check that the data is correct and then they will be used to monitor various pit latrines installed by Water For People.

Note: Afraid not great photos for this at the moment – hopefully get better ones during testing phase.