Sensor Selection in OEM Gas Detectors: Types, Accuracy, and Lifetime

In the development layout of OEM gas detector, sensors undoubtedly occupy a definite central position. It is not only an “olfactory organ” for devices to perceive the external environment, but also a key component to determine the upper limit of product functions, the positioning of shopping malls and even the life and death of brands. For OEM projects dedicated to building their own brands, sensor selection is by no means a simple purchase behavior, but a deep strategic game involving skill path, cost structure, application scenarios and whole life cycle management. Choose the right sensor, and the product will have an accurate and reliable soul; Wrong choice, even if the shell is exquisite and the algorithm is advanced, it will eventually be eliminated by the mall because of frequent false positives or sudden decline in life expectancy.

The diversity of gas detection skills determines that no “universal sensor” can cover the whole world. The primary task of OEM planning is to accurately match the most suitable skill path according to the chemical characteristics of the policy gas and the severity of the application scenario. Electrochemical sensor is the mainstream choice of portable detector at present, especially suitable for the detection of toxic gases such as carbon monoxide and hydrogen sulfide and oxygen. Its advantages are high precision, good linearity and extremely low power consumption, and it is very suitable for battery-powered handheld devices. However, its fatal shortcoming is that its life span is limited, usually only two to three years, and it is extremely susceptible to extreme temperature, and the impact of high concentration gas may even lead to its permanent “poisoning”. Therefore, when adopting electrochemical planning, OEM manufacturers must implant complex temperature compensation algorithms into firmware and plan the impact protection mechanism.

In contrast, catalytic incineration sensor is the traditional overlord of combustible gas detection. It has sophisticated skills, low cost and good response to most hydrocarbon gases. However, its working principle depends on oxygen to participate in incineration, which means that it will be completely ineffective in an anoxic environment. What’s more, it is extremely sensitive to silicon compounds and sulfides, and once it comes into contact, it will cause irreversible poisoning, resulting in a permanent decline in sensitivity. If the customer is in an oil refinery or in an environment where there is a risk of silane leakage, it will be a disastrous decision to blindly choose catalytic incineration sensors. At this moment, we should decisively turn to infrared skills. Infrared sensor (NDIR) uses gas molecules to measure the absorption characteristics of light with a specific wavelength. Its biggest advantages are that it is “never poisoned”, does not need oxygen and has a life span of five to ten years. Although the initial cost is higher and the volume is slightly larger, its extremely low protection cost and high stability make it the first choice for high-end OEM projects under harsh working conditions. In addition, for the detection of volatile organic compounds (VOCs), photoionization detector (PID) is unique with its ultra-high sensitivity and extremely fast response at ppb level, but its lamp life is limited and disturbed by humidity, which requires sophisticated algorithm compensation. Although the low-cost MOS sensor is popular in home shopping malls, it has poor selectivity and is easily disturbed by alcohol and perfume, so it should be used with caution in professional industrial OEM projects, unless it is combined with a powerful anti-interference algorithm.

Accuracy is often the top goal for customers to measure the quality of gas detectors, but it can’t be summarized by the cold “X%” in the data manual. In the real industrial field, the challenge of accuracy mainly comes from interference and environmental drift. Many sensors have natural interpenetration sensitivity. For example, the sensor for detecting carbon monoxide may also react to hydrogen. If multiple gases coexist in the field, the reading will be seriously distorted. Excellent OEM planning must eliminate this disturbance through multi-sensor fusion skills or physical filtering layer. What is even more subtle is the temperature and humidity drift. The low-end plan is often calibrated only at the standard room temperature. Once it enters the high temperature, high humidity or extremely cold environment, the reading will go a long way. Real and competitive OEM products must be calibrated at multiple points in the whole temperature range, and the high-precision temperature and humidity compensation algorithm must be written into the firmware center. In addition, the preciseness of calibration directly determines the factory accuracy, and multi-point calibration of standard gas in automatic production line should become a standard, not a dispensable ornament.

The service life of sensors is the invisible battlefield of OEM project after-sales cost and customer satisfaction. In addition to electrolyte drying or catalyst deactivation caused by natural aging, the erosion of life expectancy by environmental factors is often underestimated. Exposure to extreme temperature, high humidity or air containing toxic substances for a long time will accelerate the attenuation of sensor function. Therefore, modern OEM planning should not only be forced to wait for sensor failure, but also have the ability of active “health diagnosis”. By real-time monitoring the parameters of the sensor, such as the substrate current and the energy attenuation of the light source, the equipment should be able to warn the user to replace the sensor in advance, and change “repair after failure” into “speculative protection”. Together, modular planning allows users to replace sensor plug-ins by themselves, which not only prolongs the service life of the whole machine, but also greatly improves the user experience. For OEMs, strict inventory management is also very important. Sensors have a clear shelf life. Following the “first-in, first-out” principle to prevent the use of outdated components to assemble new machines is the bottom line to ensure the initial function of products.

In the selection strategy, OEM manufacturers should not fall into a simple cost trap. Although the sensor accounts for a large part of BOM cost, it is the soul of the product. In order to save a few dollars, the defective sensor is selected, and the false positive and false negative caused by it are enough to destroy the brand reputation instantly. The correct way is to adhere to the principle of “scene decision skills” and introduce different combinations for different sub-shopping malls: providing high-end explosion-proof plans of “infrared+electrochemistry” for petrochemical industry, high cost-effective plans of “catalysis+electrochemistry” for general manufacturing industry, and MOS plans optimized by algorithms for home shopping malls. Together, to establish the concept of “combining soft and hard”, the hardware determines the upper limit of the function, while the software algorithm determines the lower limit. Investing resources to develop advanced signal processing skills can make the sensor with medium function perform well.

In the end, successful sensor selection is the perfect balance between function, cost, life span and application scenarios. It requires OEMs not only to have keen insight into shopping malls, but also to have deep skill accumulation and life-cycle thinking. Only when each sensor is placed in the most suitable position, supplemented by precise engineering planning and intelligent algorithm, can the gas detector truly become a solid defense place for caring for life and be invincible in the fierce competition in shopping malls.