Delta-T - Model AP4 - Leaf Porometer
From Plant Science
The AP4 Leaf Porometer measures diffusion conductance by comparing the precise rate of humidification within a small cuvette (chamber) to readings obtained with a calibration plate. The plate has 6 diffusion conductance settings whose values have been accurately determined by finite element analysis.
Quoted accuracy figures for other porometers and gas analysis systems are based on time-consuming laboratory set-up and calibrations which bear little comparison to field conditions. In contrast, the AP4 Leaf Porometer features simple direct calibration in the field against a tested physical standard.
The AP4 Leaf Porometer has many other features designed to ensure that accurate, reproducible readings can be taken as easily as possible:
- Sophisticated temperature compensation
- Unstirred leaf chamber minimises unwanted stomatal closure
- Lightweight ergonomic sensor head
- Large clear LCD display (8 lines by 40 characters)
- Full QWERTY keypad for annotating up to 1500 readings
- A rugged and reliable tool for phenotyping projects
- Over 2,000 Delta-T porometers in use worldwide
Porometer design collaboration with Prof John Monteith
Delta-T Devices worked closely with Professor John L. Monteith (1929 - 2012) over a period of four decades - from manufacture of the world's first automatic porometer in the 1970s, through several subsequent versions - leading to the current AP4 Porometer.
Delta-T Devices Founder, Ed Potter, shared a platform with a number of speakers to pay tribute to Professor John L. Monteith at the 2013 American Society of Agronomy Annual Meeting in Tampa, Florida. The talk included a history of the development of the automatic porometer.
- Resolution varies with the magnitude of the value obtained. The range shown corresponds to the reading range. In relative terms, the resolution is better than 2%, but at least the smallest amount shown.
- The stated accuracy applies over the range of the calibration plate and for optimum cup conditions, i.e. from +10 to -5 °C difference between actual cup temp. and that existing at calibration, and for +2.5 to -2.5 °C difference between leaf and cup temperatures.
- Spectral and cosine responses are approximate only.
- Ambient pressure may be read from a Wristwatch Barometer type PBR1.
- Cycling at extreme combinations of temperature, conductance and RH level may not always be possible.