Technical Manual for the. Porometer type AP4. Version 4. Delta-T Devices 1 The PSB2 battery is not compatible with AP4 Porometers supplied before 2004, The AP4 Porometer. The AP4 measures the stomatal conductance or resistance of a plant leaf. It measures the time it takes for a leaf to release sufficient.The AP4 Porometer makes accurate, repeatable and convenient field measurements of stomatal conductance using the cycling diffusion principle. When combined with The AP4 cycling porometer is used for measuring the stomatal resistance of plant leaves. Download the AP4 Technical Manual from delta-t.co.uk Download Delta-T - Model AP4 - Leaf Porometer - Manual. The AP4 is a cycling porometer. It is used for measuring the stomatal resistance of plant leaves. User Manual for the. Porometer type AP4. DELTA-T DEVICES. AP4-UM-3. Page 2. Page 3. Page 4 See Appendix E: AP4 BATTERY DESIGN CHANGE. Page 96. Page 97 AP4. POROMETER. USER MANUAL. Document code: AP4-UM-3 Revised January 2004. Nick Webb Two porometer cup shapes are provided for different leaf shapes. Introduction Introduction The AP4 cycling porometer is used for measuring the stomatal resistance of plant leaves. This is a measure of the resistance to loss