Ozone Meter: What You Need to Know before Purchase
The ozone meter utilizes the ultraviolet absorption method, wherein a consistent ultraviolet light source is utilized to generate ultraviolet light. A light wave filter allows only 253.7nm wavelength of ultraviolet light to pass while filtering out other wavelengths of ultraviolet light.
This ultraviolet light passes through the sample photoelectric sensor and the ozone absorption tank before reaching the sampling photoelectric sensor. By comparing the electrical signals generated by the sample photoelectric sensor and the sampling photoelectric sensor, and applying a mathematical model, the concentration of ozone can be determined.
Ozone exhibits high chemical reactivity, and its liberated energy can instantaneously cause strong oxidation, leading to sterilization, disinfection, and detoxification. Ozone is extensively employed for sterilizing water, disinfecting tableware, purifying indoor air, preserving fruits and vegetables, disinfecting clothing, and in medical treatment. Nonetheless, excessive ozone concentration can be extremely detrimental to human health. Thus, monitoring ozone concentration is essential to leverage its potent oxidizing properties while preventing its hazardous effects.
What is an Ozone Meter?
The most efficient means of detecting ozone concentrations is through an ozone meter. This device converts information on the composition and concentration of ozone gas present in the surroundings into a format that can be utilized by personnel, instruments, computers, and other systems.
Ozone Meter’s Working Principle
Ozone meters can be categorized into three primary types based on their detection principles, namely ultraviolet, semiconductor, and electrochemical.
Studies indicate that ozone has a high absorption coefficient for 253.7nm UV light, which is attenuated by ozone in compliance with Lambert-Beer's law. Ozone gas meters operate on the principle of UV absorption, utilizing a stable UV light source to generate UV light. The filter only permits 253.7 nm UV light to pass by blocking other wavelengths of UV light. After traversing the sample photoelectric sensor, the UV light is absorbed by the ozone before reaching the sampling photoelectric sensor. By contrasting the electrical signals generated by the sample photoelectric sensor and the sampling photoelectric sensor, the concentration of ozone is determined using the Lambert-Beer approach.
2. Semiconductor Ozone Meter
Gas-sensitive semiconductor materials, such as WO3, Sn0, In2O3, and other oxide sheets, are utilized in semiconductor ozone sensors. These materials undergo a redox reaction when they absorb ozone, producing or emitting heat, leading to a corresponding shift in the temperature of the element and a change in its resistance. The concentration of ozone is transformed into an electrical signal to quantify the ozone concentration. As a rule, when the concentration rises, the element's resistance also increases significantly and remains linear over a certain range.
An electrochemical ozone sensor comprises a working electrode, counter electrode, reference electrode, electrolyte, and circuit system. A steady potential value can be sustained between the working electrode and the reference electrode. When ozone permeates the sensor, the reduction reaction arises at the working electrode and the oxidation reaction at the counter electrode, generating a minute current between the counter electrode and the working electrode. This current enters the sensor and corresponds to a certain range of ozone concentration, which is ultimately processed by the circuit system to compute the ozone content.
Tips for Selecting an Ozone Meter
When purchasing an ozone meter, it is critical to determine the characteristics of the usage environment and the intended application. Ozone monitoring equipment should be selected based on its stability, sensitivity, selectivity, corrosion resistance, and other features.
1. Stability pertains to the consistency of the sensor's fundamental response over its operational lifespan and is influenced by zero drift and interval drift. Zero drift is the alteration in the sensor's output response over its operating time when ozone is absent. Interval drift is the reduction in the sensor's output signal when it is continuously exposed to ozone and is conveyed as a drop in the signal output over the operating time. Ideally, the annual zero drift for sensors in uninterrupted operating circumstances should be below 10%.
2. Sensitivity denotes the ratio of the sensor output alteration to the measured input change and chiefly relies on the technology employed in the sensor structure. The majority of gas sensors employ biochemical, electrochemical, physical, and optical principles. The primary consideration when selecting a sensitive technology is to ensure that it is capable of detecting the target gas's threshold limit value (TLV) or the lower explosive limit (LEL) percentage with sufficient sensitivity.
3. Selectivity, also known as cross-sensitivity, is determined by measuring the sensor response generated by a particular concentration of interfering gas, which is comparable to the sensor response generated by a specific concentration of ozone. This characteristic is vital in applications that monitor multiple gases since cross-sensitivity can decrease the measurement's reliability and repeatability. The perfect sensor should possess high sensitivity and high selectivity.
4. The ability of the sensor to resist corrosion when exposed to high volume fraction target gases is referred to as corrosion resistance. When a large amount of gas is leaking, the probe should be able to withstand 10-20 times the expected gas volume fraction. Under normal operating conditions, the sensor drift and zero calibration values should be as small as possible to ensure its reliability and accuracy.
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