For full details refer to the. AP4 User. Manual Using the. AP4. Porometer. Calibration process. Taking a measurement. Downloading to a PC 1) Porometer calibration. The AP4 is supplied with a moulded polypropylene calibration plate with six groups of holes; the rate of diffusion of water vapour throughUser Manual for the. Porometer type AP4. DELTA-T DEVICES. Y 3 to have the same settings at the AP4 and printer. These settings are changed in the The AP4 Porometer measures the stomatal conductance or resistance of plant conductance or stomatal Install calibration data. Put leaf in head. Se 1 e c t I START I. The AP4 starts taking readings. the reading. Nitrate sap content can be measured by a hand-held reflectometer (e.g., the Nitrachek and the RQflex) according Dynamic diffusion leaf porometer (e.g., AP4). Simple and rapid calibration in the field. 0 Minimises leaf stress during measurement. 0 Outstanding value and ease of use. AP4 Porometer. PRODUCT