Infrared thermometer principle structure
The infrared light received from the object to be measured is focused by a lens through a filter on a detector. Detector through the measured object radiation density of the integral, produce a current or voltage signal proportional to the temperature, in the electrical components connected hereafter, the temperature signal linearization, emissivity region of the correction, and converted into a standard output signal.
In principle, there are two kinds of portable pyrometer and fixed pyrometer, therefore, the following features will be the main in choosing the right infrared pyrometer for different measurement points:
1. Sighting
Sight has this role, the pyrometer refers to the measurement of the block or measurement point can be seen, a large area of the measured object can often do not sight. In the small measured object and more distant measurement distance, the sight in the form of a lens with a dashboard scale or laser pointing point is recommended.
2, lens
Lens to determine the measured point of the pyrometer, for large objects, generally with a fixed focal length of the pyrometer can be enough. However, in the measurement distance away from the focus point, the image of the edge of the measurement point will not be clear. For this reason, the use of zoom lens is better, in the zoom range given, the pyrometer can be adjusted to measure the distance, * new pyrometer with a zoom interchangeable lenses, near lens and far lens can be replaced without calibration review.
3, the sensor, that is, the spectral receiver
Temperature is inversely proportional to wavelength. In the low object temperature, the long-wave spectral region of the sensitive sensor (thermal film sensor or thermoelectric sensor) is very suitable, at high temperatures, will use the short-wave sensitivity affected by germanium, silicon, indium - gallium and other components of the photoelectric sensor.
When selecting the spectral sensitivity, the absorption spectral bands for hydrogen and carbon dioxide are also taken into account. In a certain wavelength range, that is, the so-called "atmospheric window", H2 and CO2 to infrared is almost penetrating, so the thermometer's light sensitivity must be in this range, in order to exclude the effect of atmospheric concentration changes, in the measurement of thin films or glass, but also to take into account that these materials are not easy to penetrate within a certain wavelength. In order to avoid the measurement error caused by the background light, the use of appropriate, only to receive the surface temperature of the sensor, the metal has this physical property, the emissivity increases as the wavelength decreases, experience and talk about the measurement of the temperature of the metal, the general choice of the * short measurement wavelength.
