Plant respirometer permits high resolution of relatively small changes in the rate of oxygen consumed by plant organisms undergoing oxidative metabolism in a nonphotosynthetic state. The two stage supply and monitoring system operates by a differential pressure transducer and provides a calibrated output by digital or analog signals

Foster, D. L.

English

NASA Technical Reports Server

September 1966
	 Brief 66-10406 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U. S. space 
program and to encourage their commercial application. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Plant Respirometer Enables High Resolution of Oxygen Consumption Rates 
Solenoid Valve
Pressure-Range 
	
Pressure	 Control Switch 
Regulator 
Pressure Regulator
Specimen 
Primary
	 Chamber 
Oxygen 
Supply
Secondary Supply	
Analog Recorder 
Differential Pressure Transd 
	
Subcarrier Oscillator-	
Frequency Counter
 Jr 
The problem: 
To devise an apparatus that will permit high reso-
lution of relatively small changes in the rate of oxygen 
consumed by plant organisms undergoing oxidative 
metabolism in a nonphotosynthetic state. 
The solution: 
A two-stage supply and monitoring system consist-
ing of primary and secondary oxygen supply cham-
bers, a chamber for the plant specimen, a solenoid 
valve in the supply line between the primary and 
secondary chambers, a differential pressure transducer 
between the secondary supply chamber and the speci-
men chamber, and a pressure-range control switch
connected between the differential pressure transducer 
and the solenoid valve. The output from the differen-
tial pressure transducer, representing the relatively 
small changes in the oxygen consumption rate, may 
be read out as an analog signal on a strip chart 
recorder or as a digital signal by means of a frequency 
counter. 
How it's done: 
The primary chamber is charged with a sufficient 
supply of oxygen to provide for the metabolic needs 
of the plant organism during the investigative period. 
A pressure regulator maintains the outlet pressure 
ANIL	 (continued overleaf) 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately owned rights.
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from this supply at approximately 820 mm Hg abso-
lute. The solenoid valve controls the flow of oxygen 
from the primary to the secondary supply chamber. 
The outlet pressure regulator from the secondary 
supply chamber is set to maintain a constant pressure 
of 770 mm Hg absolute in the specimen chamber. The 
differential pressure transducer provides an output 
signal ranging from 0 to 5 vdc for a differential pres-
sure range of 0 to 0.3 psi. The dc output signal 
triggers a specially developed solid state switch for 
opening the solenoid valve when the pressure differ-
ential between the specimen chamber and the sec-
ondary supply chamber approaches zero. This valve 
remains open, allowing oxygen to flow from the 
primary to the secondary supply chamber, until a 
pressure differential of 0.3 psi (786 mm Hg absolute 
pressure in the secondary chamber and 770 mm Hg 
absolute pressure in the specimen chamber) has been 
reestablished, at which time the valve is automatically 
closed. The 0 to 5 vdc signal from the differential 
pressure transducer is also fed to an analog recorder 
or used to modulate a subcarrier oscillator connected 
to a frequency counter. The recorder or counter is
calibrated to give a readout of the rate of oxygen con-
sumption in the specimen chamber corresponding to 
the rate of pressure change in the secondary supply 
chamber. 
Note: 
Inquiries concerning this invention may be di-
rected to:
Technology Utilization Officer 
Headquarters 
National Aeronautics and Space 
Administration 
Washington, D.C. 20546 
Reference: B66-10406 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: Donald L. Foster

of Space Defense Corporation

under contract to

Headquarters, National Aeronautics

and Space Administration 
(HQ-47) 
Brief 66-10406	 Category 04


Plant respirometer enables high resolution of oxygen consumption rates

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