Most gas detection sensors use chemical reactions between their sample gas and the physical properties of the sensor for accurate gas detection, but there may be advantages in employing one that relies solely on the physical properties of the gas to achieve detection, including lower power consumption, simpler construction, faster response time and longer lifetime.
Many types of thermal gas detectors utilize this principle by setting their sensor material at a low temperature to encourage electrons to shift from their valence band into the conduction band and back again.
Catalytic Bead Detectors
Catalytic bead detectors (commonly referred to as Pellistor sensors) have long been the industry standard for flammable gas detection. A catalyst-treated sensing bead in these sensors oxidizes when combustion gases diffuse through flame arrestors, increasing temperature and altering its resistance compared with an inert reference bead; any changes are then detected by their Wheatstone bridge circuit and sent signaled back through to electronic circuitry via Wheatstone bridge circuitry.
Pellistor sensors rely on fine platinum wires embedded within their bead to conduct electrical current that detects combustible gases and oxygen levels. Over time, mechanical stress and exposure to industrial chemicals can weaken these wires, inhibiting normal oxidation reactions that should occur, leading to the accumulation of carbon coating on its catalyst that reduces its sensitivity and poisons the sensor – rendering accurate readings impossible without replacing or bump testing prior to use – so maintaining a robust, high-quality system in order to safeguard workers.
Infrared Detectors
The thermal IR gas detector is designed to detect radiant energy from objects and convert it into a signal, as well as detect any thermal radiation all objects emit. They use this energy to produce images showing variations in energy levels between objects; making it possible to see through darkness or obscured conditions.
Since the 1940s, various infrared detector materials have been created. This ranges from thermal detectors such as thermocouples and bolometers to imaging sensors like Golay cells, photodiodes, and thermopiles; many of these detectors also incorporate hazardous chemicals such as lead or cadmium.
Space applications of infrared detectors also make use of infrared detectors, previously exclusively based on mercury cadmium telluride (MCT). Unfortunately, this requires a multi-stage cryocooler which makes this type of detector bulky and costly; new PC/PV-based infrared detectors with type-II superlattices offer greater compositional uniformity over all device pixel areas than MCT detectors can offer.
Gas Detectors with OGI Technology
Undetected gas leaks can have devastating repercussions for a company’s operations, from product loss and environmental pollution to employee health risks. To combat this threat, it’s vitally important that your employees have access to tools and technologies necessary for quickly finding dangerous leaks.
Optical Gas Imaging (OGI) is an infrared camera-based technology used to visualize heat given off by escaping gases, making leaks visible against a background of cold air. OGI cameras are typically handheld video cameras with special filters used to restrict wavelengths reaching their detector, making them extremely selective and sensitive.
OGI cameras integrated into drones provide the capability of detecting gas emissions caused by leaks, including methane, butane, ethylene, and isopropyl. Their use greatly improves inspection efficiency and safety in difficult-to-access locations.
Gas Detectors with Optical Technology
These detectors use narrow-band filters to identify chemical compounds by their unique spectral signature and simultaneously detect multiple gases simultaneously.
These systems utilize sensors and cooled detectors whose radiation is filtered to only allow wavelengths related to the gas being detected to reach them, with output changing according to the concentration of gases being sensed by them.
Optic fiber gas sensors are constructed using an optical fiber with an internal or external cavity; either an intra-cavity can serve as the cavity; otherwise, an external cavity spliced onto standard single-mode fiber may be used. Intrinsic sensors use photonic crystal fiber (PCF), where holes within its fiber serve as cavities for optical emission measurement.
This sensor can detect potentially explosive and toxic gases in enclosed spaces and industrial safety settings, making them perfect for applications such as confined spaces. Handheld or stationary models exist, both featuring alarm systems to alert individuals of potentially hazardous gas presence.
