A New apparatus has been designed, which gives an accurate measurement of the rate and height of capillary rise of water in a porous material, such as fabrics, from the initial moment of contact with water.
When two parallel plate electrodes are immersed in water, the increase of capacitance across the twin electrodes is directly proportional to the height of water between the electrodes. The circuit was used to detect the level of water contained in a vertical strip of fabric put between twin parallel plate electrodes and to give a good linear relation between capacitance and water level. One of twin electrodes is a thin stainless steel plate and the other tinned wire coil mounted on glass plate, which are coated with Teflon film to keep a good insulation.
The progress of liquid rise in a fabric, thus the increase of capacitance is recorded automatically from the first moment of contact with the liquid. Such a water level-capacitance conversion method has a very quick response, and so we can obtain a real time record of the movement of water. Not only can it be used to study very rapid initial capillary rise, but we can determine the fiber surface characteristic and the fabric geometry effect from accurate results obtained.
Subsequent papers will analyze in more detail the observed transient properties.