Conventional techniques for measuring in-situ infiltration include the use of a single or double ring infiltrometer. Single and double ring infiltrometer only measures flow under ponded (saturated) conditions, and when used in soil with distinct macropores, preferential flow will dominate the flow. (See: Poiseuille's law) This does not reflect infiltration under rainfall or sprinkler irrigation. Therefore, many authors attempted to create a negative potential (tension) on the water flow. This is to exclude macropores in the flow process, hence only measuring the soil matrix flow.