Presentation on theme: "Moisture Content Measurement of Bark and Sphagnum Moss Using ECH 2 O Sensor for the Production of Phalaenopsis Wei Fang and Walter Ray Dept. of Bio-Industrial."— Presentation transcript:
Moisture Content Measurement of Bark and Sphagnum Moss Using ECH 2 O Sensor for the Production of Phalaenopsis Wei Fang and Walter Ray Dept. of Bio-Industrial Mechatronics Engineering National Taiwan University Taipei, Taiwan, ROC IHC01832
Objectives Find a sensor Establish a water content monitoring system Work on Sphagnum moss & bark
Why is it important to automatically measure water content in the media? Skillful hand-watering personnel is not easy to find/ to train. Hobby growers professional growers Increasing production area rapidly Setting up foreign branch Uniform quality requirement …etc.
Experiment of Pre-submerge Before use Treatment 1: Submerge the barks in water overnight (current practice of most growers) Treatment 2: No pre-submerge (suggested by the manufacturer) When use After filled into the pot, Watering thoroughly Allow for drain out Start recording the sensor output
Use it directly, do not submerge the bark in the water before use.
Difference due to pre-submerge in Tap water Orchiata bark #9Orchiata bark #5 Orchiata bark #8 w/ w/o
Small conclusions Pre-submerge makes little difference for bark no.8 (smallest particle) For large particle, without pre-submerge Hold little water in the beginning Dry out easily Require frequent watering If watering is conducted manually, pre-submerge will normally preferred. wash-out of add-in Dolomite
Orchiata bark #9Orchiata bark #5 Orchiata bark #8 Difference due to pre-submerge in Tap water
3 sources of Sphagnum Moss were investigated Imported from New Zealand (NZ) Chile China
Experiment of tightness of Sphagnum Moss filled in a pot
Preparation Before use Sphagnum moss was pre-submerged in tap water overnight When use Pressed until feeling moist not wet (hold with both hands) Fill the pot with moist sphagnum moss Watering thoroughly Allow for drain out Start recording the sensor output
Difference due to tightness of NZ Sphagnum Moss filled into a pot Photos taken after the experiment tight loose
Difference due to tightness of Chile Sphagnum Moss filled into a pot
Difference due to tightness of China Sphagnum Moss filled into a pot
Sp. Moss from Chile has the greatest water holding capability when loosely filled. When loosely filled, 3 types of moss performed quite differently. China Chile Difference due to sources of loosely filled Sphagnum Moss Sp. Moss from China has the greatest mV output due to high EC of dissolved water.
Small conclusions Some SOPs are required to fill the pot when using Sphagnum Moss as growth media. Fixed amount of Moss for fixed size of pot is preferred. Tightly filled is preferred. Water holding capability Chile > NZ > China Sphagnum Moss
Conclusions ECH 2 O-10 and ECH 2 O-5 can be used to continuously monitor the water content of media used in growing Phalaenopsis. (ECH 2 O-5 is EC insensitive in the range of 0~2.21 mS/cm) Converting equations were derived for 3 sources of Sphagnum Moss and 3 sizes of Orchiata bark.
What is Permittivity ? The permittivity of a medium is an intensive physical quantity that describes how an electric field affects and is affected by the medium. Permittivity can be looked at as the quality of a material that allows it to store electrical charge. A given amount of material with high permittivity can store more charge than a material with lower permittivity.
What is dielectric constant ? The dielectric constant ε r is defined as the ratio: ε r = ε s / εo = ε s / ( 8.85 x 10 -12 F/m) = ε s x 1.13 x 10 11 Where ε s : the static permittivity of the material in question, ε 0 : the vacuum permittivity. This permittivity of free space is derived from Maxwell's equations and is equals the ratio D/E in vacuum, where D is the electric flux density and E is the electric field intensity. In vacuum (free space), the permittivity ε s is just ε 0, so the dielectric constant is unity.
Dielectric constant of some materials at room temperature MaterialDielectric constant Vacuum1 (by definition) Air1.0005 Teflon2 Paper3 Soil Minerals4 Rubber7 Methyl Alcohol30 Water80 Barium Titanate1200