AP4 Leaf Porometer features

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.

Parameter	Reading range	Resolution [1]	Accuracy [2]	Test conditions [5] Reading range
Conductance	5.0 -1200 mmol m-2 s-1	0.1 – 10	± 10 %	5 – 800 mmol m-2 s-1
			± 20 %	800 – 1200 mmol m-2 s-1
Conductance	0.25 – 30.0 mm s-1	0.01 – 0.1	± 10%	0.25 – 20 mm s-1
			± 20 %	20-30 mm s-1
Resistance	0.2 – 40 s cm-1	0.01 – 0.1	± 10 %	0.5 – 40 s cm-1
			± 0.2 s cm-1	0.2 – 0.5 s cm-1
RH	0 – 100%	0.1	± 4%
Cup temp	-5 – +55 °C	0.1	± 0.7 °C	0 – 50 °C
Cup-leaf temp	-5 – +5 °C	0.1	± 0.2 °C	0 – 50 °C
PAR flux [3]	0 – 2500 µmol m-2 s-1	10	± 15%
Pressure [4]	600 – 1200 hPa, settable in steps of 5 hPa
RH cycle level	20 – 80 %RH, settable in steps of 5%

[1] 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.
[2] 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.
[3] Spectral and cosine responses are approximate only.
[4] Ambient pressure may be read from a Wristwatch Barometer type PBR1. 
[5] Cycling at extreme combinations of temperature, conductance and RH level may not always be possible.

Channel science and technology has been dedicated to the teaching, scientific research and the sales, research and development of applied instruments in the fields of soil, plants, environment, hydrology, meteorology and animal physiology, ecology and environmental hydrology for many years.