GB1143403A - Apparatus for supplying carbon dioxide to growing plants - Google Patents

Abstract

1,143,403. Treating plants. NATIONAL DEVELOPMENT CORP. 4 May, 1966 [4 Feb., 1965], No. 4958/65. Heading A1E. [Also in Divisions G1 and G3] Horticultural apparatus including a chamber in which plants may be grown and a source of carbon dioxide connected to the chamber comprises means for sensing the concentration of carbon dioxide in the chamber and automatic control means for adjusting the rate of supply of carbon dioxide to the chamber from the source in dependence upon the concentration sensed. As illustrated the introduction of carbon dioxide into the chamber 1 from the source 3 is controlled by a valve 5 which is controlled in dependence or the concentration sensed by an automatic control 34. The sensing means comprises a pump 6 which draws off samples of the atmosphere in the chamber and introduces the sample in the form of bubbles into a tube 9 which contains substantially pure water, a conductivity sensing cell 15 and a chamber 26 containing ion exchange resin which de-ionises the water. The carbon dioxide is absorbed by the water in the tube 9 and bubbling of the sample will cause water to overflow into vessel 16. The conductivity of the water in the vessel 16 will vary according to the concentration of carbon dioxide therein, and the conductivity is measured by passing an electric current between electrodes 23, which together with the ionised water form one limb of a pontential divider circuit contained in the control 34. The resistance of the other limb is adjustable in accordance with a set value input 35 which may be set manually or automatically by a timer or temperature or solar radiation. If the rate of bubble flow falls below a predetermined value, thus indicating a failure in the supply of carbon dioxide, a photosensing device 31, 32 will cause, through control 34, the valve 5 to be closed.