Compact portable indicator-meter of ozone concentration

Abstract

Compact portable indicator-meter of ozone concentration is the most suitable device to measure the ozone concentration in the work zone and control its maximum allowable concentration. The analysis of existing ozone measurement methods showed that the amperometric method is the most suitable for designing such indicators-meters. Accordingly, two-electrode electrochemical ozone sensors of the amperometric type based on solid and liquid electrolyte are selected as the primary measuring detectors. Studies of possible schemes for constructing input circuits of the indicator-meter showed that it is advisable to connect an ozone sensor with a solid electrolyte directly to the input of an operational amplifier functioning in a current-voltage converter mode without a load resistor. The ozone sensor with a liquid electrolyte is better to connect to a load resistor of 100 Ohms, the signal from which is fed further to the input of an operational amplifier functioning in a voltage converter mode. The structural and schematic diagrams of the ozone concentration indicator are developed and an experimental sample is made. It is calibrated at 4 mg/m3 point using an electrochemical ozone generator. The ozone concentration produced by an electrochemical generator is tested using the iodometric method and the error does not exceed 5 %. The experimental study of the errors of the indicator-meter of ozone concentration with a sensor based on solid electrolyte was conducted in the main measurement range, taking into account its higher sensitivity and lower error of nonlinearity, compared with the sensor based on liquid electrolyte. The experimental study of the errors of the ozone concentration indicator-meter with a sensor based on a liquid electrolyte is conducted in an extended measurement range. For the tests, two series of studies are conducted with an interval of 1,5 months, which made it possible to establish changes in the sensor characteristics. The study results of two variants of an experimental sample of the ozone concentration indicator-meter with solid and liquid electrolyte sensors showed that the relative measurement error does not exceed 25 % in the ozone concentration range of 0,1-10 mg/m3. And in the range of 0,05-0,5 mg/m3 the error value from full scale does not exceed 22 %. These values correspond to the existing standards.