Wash Monitoring System

Unilever manufactures a wide range of consumer products, including detergents.

Availability of a high performance system for measuring the progress of textile wash processes in a domestic washing machine is of great importance for research on detergents and rinse conditioners. Commercially available general purpose data-loggers can be used for some simple experiments in the drum of a washing machine, like temperature measurements. However, wash process monitoring requires accurate measurement of the values of large set of variables and use of dedicated sensors and measuring techniques.

The system consists of a novel embedded sensor system, as a part of the 'washdisc' for sensing, measuring and data-collection. It was tested in a front-loading automatic (domestic) washing machine and used for monitoring the key physical-chemical parameters of a wash process, such as acidity, conduction, concentration of sodium and calcium and turbidity.

Involvement of LioniX

Development of the system for measuring the progress of a wash process in the drum of a consumer washing machine:

• The turbidity sensor is based on an optical dual ratio principle.
• For the electrical conductivity sensor and the pH sensor, existing sensors - developed by the MESA+ Institute from the University of Twente - were used and adapted to this application and the harsh environment. The pH is measured using an ISFET (Ion Sensitive Field Effect Transistor).
• For the sodium and calcium sensors, the pH sensors were modified by applying ion-selective membranes (CHEMFET: Chemically Modified Field Effect Transistor).
• Development of a sensor packaging technology resistant against the harsh circumstances inside the washing machine (environment with soap, changing wet and dry conditions and high temperature).
• Development of the analogue low power electronics for transformation of the sensor signals into standard readable data.

This project was carried out with the following partners:

• Application: Unilever Research Vlaardingen
  
• Digital electronics and server software: TNO-TPD
  
• Water sampling and housing: TNO-Industrie
  
• Sensors and sensor electronics: LioniX
  

References

Columbus: A Novel Sensor System for Domestic Washing Machines, Sensors Magazine