Temperature Sensor Buying Advice
Temperature sensors are specially designed devices to detect the temperature or humidity of certain objects or area. The intensity of an object's discharged Infrared radiation energy increases or decreases in proportion to its temperature. It is the emitted energy, measured as the target's emissivity, which indicates an object's temperature. Emissivity is a term that is used to specify the quantity of the energy-emitting characteristics of different materials and surfaces. IR temperature
sensors have adjustable emissivity settings, which allow accurate temperature measurements of several surface types.
The radiated energy comes from an object and reaches the IR sensor through its optical system, which focuses the energy onto one or more photosensitive detectors. The detector then converts the IR energy into an electrical signal, which is in turn converted into a temperature value based on the sensor's calibration equation and the target's emissivity amount. This temperature value can be displayed on the sensor, or, in the case of the smart sensor, converted to a digital output and displayed on a computer screen.
There are differences existed between different temperature sensors or temperature measurement device types. From one point of view, they can be simply classified into two groups, contact and non-contact. On the current market, there are vendors of each temperature sensor type, some vendors sell more than one type and some sell nearly all types, but not always all brands. There are differences between brands and the differences are most evident among those device types for which there are few if any recognized
standards. You can probably start your hunting journey either for a specific temperature sensor type or go to the vendor page index and you can access the vendors of specific types from there.
Both contact and non-contact sensors require some assumptions and inferences in use to measure temperature. Remember the truism that all sensors have errors in their readings. One key secret to high quality measurement results is to have confidence in the error estimates. Neglecting to make a careful error analysis can result in error much larger than the assumed values. It is worth noting that all competent error analyses start with the uncertainties assigned to the traceable calibration of the sensor itself.
Without traceable calibration, one is forced to make assumptions.
Contact temperature sensor infers the temperature of the object to which the sensor is in contact by assuming or knowing that the two are in thermal equilibrium, that is, there is no heat flow between them.
Most commercial and scientific non-contact temperature sensors measure the thermal radiant power of the Infrared or Optical radiation that they receive from a known or calculated area on its surface, or a known or calculated volume within it.
One then infers the temperature of an object from which the radiant power is assumed to be emitted (some may be reflected rather than emitted). Sometimes the inference requires a correction for the spectral emissivity (NB: the two words, spectral & emissivity, are used together in correcting IR Thermometer readings -the "emissivity", unspecified, is a big trap which even some of the suppliers of devices and calibration equipment fall into unwittingly for a variety of reason about which one can only
speculate) of the object being measured.
Knowing how and when to apply a spectral emissivity correction is part of the inference, too, and can introduce significant errors if not done correctly. See our Trip down the E-missivity Trail to help you understand that aspect a little better.
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