Hi John, yes the pressure heads will make a difference when you are making measurements in high permeability vs low permeability soils. You need to have enough of a difference in the infiltration rates at the two pressure heads in order to accurately calculate the sorptivity and correct for 3-dimensional flow. For low permeability soils, we recommend a higher pressure head difference, typically 10 or 15 cm. For high permeability soils, it is best to use a smaller pressure head difference, between 2 and 10 cm. We recommend more cycles when you are making measurements in initially drier soil to allow for the measurements to reach a quasi-steady state. If the soil is wetter and closer to field capacity you can use fewer measurement cycles. If you have any further questions feel free to reach out to our customer support team at support.environment@metergroup.com.
Does it matter what high head or low head you select? Also, does it matter how many cycles you do?
Hi John, yes the pressure heads will make a difference when you are making measurements in high permeability vs low permeability soils. You need to have enough of a difference in the infiltration rates at the two pressure heads in order to accurately calculate the sorptivity and correct for 3-dimensional flow. For low permeability soils, we recommend a higher pressure head difference, typically 10 or 15 cm. For high permeability soils, it is best to use a smaller pressure head difference, between 2 and 10 cm. We recommend more cycles when you are making measurements in initially drier soil to allow for the measurements to reach a quasi-steady state. If the soil is wetter and closer to field capacity you can use fewer measurement cycles. If you have any further questions feel free to reach out to our customer support team at support.environment@metergroup.com.