SIR Model S-5014 ozone analyser is a self-contained instrument which measures the concentration of ozone in a sample of ambient background) gas, such as air, oxygen, nitrogen, etc.
This instrument is a monochromatic, U.V. absorption spectrophotometer specific to ozone. The analyser measures ozone concentration directly by the attenuation of U.V. radiation by ozone molecules in the optics cell. The ozone concentration is obtained by measuring the relative intensity of transmitted U.V. radiation for a "measurement pair" consisting of a consecutive zero and sample gas cycle.
A fixed quantity of "zero gas" and the same quantity of "sample gas" are alternately drawn into the instrument's optics cell by utilizing a pump and sample handling system. The zero (reference) gas is ambient gas, with the ozone "scrubbed" (removed) by a catalytic converter; the sample gas is unaltered ambient gas with the ozone still present.
Alternate, consecutive measurements of the absorption of U.V. radiation during the reference cycle and the measurement cycle are made by the photometer. Continuous auto-zeroing and removal of interferences are accomplished by this paired measurement technique, which may be thought of as "gas chopping”. This technique achieves the same zero stability, with the added advantage of inherently eliminating all the interferences and a non-existing zero drift.
Span stability is achieved by ensuring that the reference and measurement cycle times for each measurement pair are identical. A special "clock/counter control circuit (much like a stopwatch) is utilized. This circuit is first set by the reference cycle time interval, and then controls the subsequent measurement cycle fime interval. It is then reset for the measurement pair.
Appropriate signal processing of each individual measurement pair by the electronic system yields the instantaneous ozone concentration (within the selected update cycle time of the instrument) in accordance with the Beer-Lambert law.
MODEL S-5014 UV Absorption O3 Analyzer
