Pak Choi Handbook

Sensors

Temperature
Recommended Sensor : Resistance Temperature Detector (RTD) located in an Aspirated Box.

Listing of system components and their manufacturers.
Note: References to company and brand names are used for identification purposes only and do not necessarily constitute endorsements over similar products made by other companies.

Dissolved Oxygen Sensor
Model:	Orion 820, hand held, battery operated
Manufacturer:	Orion Research, Inc., Boston , MA
Specifications:	Output: 10 mV per mg/l Response time: 99% of final value in less than 40 sec at 20C Min. sample flow: 15 cm/sec Temp. range: 0 - 50^oC Membrane: Teflon^Æ FEP, thickness: 12.5 microm

Compact Submersible Centrifugal Pump

Model:

1P808A

Manufacturer:

Teel

Distributor:

Dayton Electric Mfg. Co., Chicago, IL

Specifications:

0.02 HP, 75 W, max 1.5 Amps
flow rate versus pressure head:

rate

head

(l/min)

(kPa)

25.2

3.0

21.4

9.0

18.9

14.9

11.4

26.9

max head: 32.9 kPa

Solenoid Valve

Model:

U8225A3V: Brass solenoid valve (normally closed)

Manufacturer:

Automatic Switch Co., Florham Park, NJ

Temperature Sensor (for temperature of nutrient solution)

Model:

PR-11-2-100-(1/4)-6-E

Manufacturer:

OMEGA Engineering, Inc., Stamford, CT

Specifications:

100 Ohm resistance temperature probe with 2 lead wires

Relative Humidity
Recommended Sensor : Accuracy and stability of the sensor are important for reliable performance in the relatively harsh greenhouse environment.

Carbon Dioxide Concentration
Recommended Sensor : Infra Red Carbon Dioxide Sensor

Light

Recommended Sensor : Quantum Sensor measuring Photosynthetically Active Radiation (PAR, 400-700 nm wave band). Foot candle sensors and lux meters are inappropriate, because they are used to quantify the sensitivity of the human eye and do not necessaily measure light used for photosynthesis.

Dissolved Oxygen (DO)

Recommended Sensor : Reliability and easy maintenance are important for this delicate sensor.

Electrical Conductivity (EC)

Recommended Sensor : Reliability and easy maintenance are important for this delicate sensor. This sensor is sometimes combined with a pH sensor in one unit.