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A typical calibration schedule for a portable gas detector is a daily "bump test" accompanied by a monthly calibration. [17] Almost every portable gas detector requires a specific calibration gas In the US, the Occupational Safety and Health Administration (OSHA) may set minimum standards for periodic recalibration. [citation needed]
Sensors are usually designed so that the gas supply is limited by diffusion, and thus the output from the sensor is linearly proportional to the gas concentration. This linear output is one of the advantages of electrochemical sensors over other sensor technologies (e.g. infrared), whose output must be linearized before they can be used.
A nondispersive infrared sensor (or NDIR sensor) is a simple spectroscopic sensor often used as a gas detector.It is non-dispersive in the fact that no dispersive element (e.g a prism or diffraction grating as is often present in other spectrometers) is used to separate out (like a monochromator) the broadband light into a narrow spectrum suitable for gas sensing.
An open path detector usually costs more than a single point detector, so there is little incentive for applications that play to a point detector's strengths: where the point detector can be placed at the known location of the highest gas concentration, and a relatively slow response is acceptable. The open path detector excels in outdoor ...
All of these have the same basic design of two electrodes separated by air or a special fill gas, but each uses a different method to measure the total number of ion-pairs that are collected. [1] The strength of the electric field between the electrodes and the type and pressure of the fill gas determines the detector's response to ionizing ...
The device, also called a combustible gas detector, operates on the principle of resistance proportional to heat—a wire is heated, and a sample of the gas is introduced to the hot wire. Combustible gases burn in the presence of the hot wire, thus increasing the resistance and disturbing a Wheatstone bridge , which gives the reading.
A detector for propane is best placed down low near the floor, as propane is heavier than air. [3] A detector for natural gas (city gas) is best placed up high, near the ceiling. [3] Some detectors can detect both natural gas or propane, but this requires a compromise location. [4]