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pyrometer BP21
Information about the device
Device description
The pyrometer
BP21
uses an infrared sensor to measure
surface temperatures without contact. An integrated dual laser
pointer can be switched on for the precise determination of the
measuring spot diameter.
In addition, you can set the degree of emission of the material to
be measured which will result in a more precise measurement
result.
The device further features an alarm function. When exceeding
or falling below the specified values, the device emits an
acoustic signal.
Moreover, the device can indicate either the highest or lowest
value of the measurement.
The display can be illuminated as needed. An automatic switch-
off function saves the battery when not in use.
Measuring principle
The device measures the temperature by means of an infrared
sensor. Important factors playing a role in the temperature
measurement are the measuring spot diameter and the degree
of emission.
Measuring spot
Observe the ratio of the distance (D) to the measuring spot
diameter (S). The larger the distance to the object, the larger the
measuring spot diameter and hence, the less precise the
measured result, for the device calculates an average
temperature from all the temperatures in the measuring spot.
Spot
12.5 mm
100 mm
Distance
150 mm
1200 mm
D:S = 12:1
Laser
Infrared
Degree of emission
The degree of emission is used to describe the energy radiation
characteristics of a material.
Most organic materials have an emissivity of 0.95. Metals or
shiny materials come with a much lower value.
A material's emissivity depends on various factors, e.g. on
•
Material composition
•
Surface condition
•
Temperature
The emissivity can range between 0.1 and 1 (in theory).
The following rule of thumb can be assumed:
•
When a material is rather dark and its surface texture matt,
it probably has a high emissivity.
•
The brighter and smoother the surface of a material, the
lower will be its emissivity, presumably.
•
The higher the degree of emission of the surface to be
measured, the better it is suited for non-contact
temperature measurement by use of a pyrometer or
thermal imaging camera, since falsifying temperature
reflections become negligible.
Nevertheless, entering a degree of emission as appropriate as
possible is indispensable for a precise measurement.
Material
Degree of emission
Aluminium, roughened
0.1 to 0.3
Aluminium, alloy A3003,
oxidized
0.3
Aluminium, oxidized
0.2 to 0.4
Asbestos
0.92 to 0.95
Tarmac
0.92 to 0.95
Basalt
0.7
Concrete
0.92 to 0.95
Bitumen
0.98 to 1.00
Lead, oxidized
0.2 to 0.6
Lead, rough
0.4
Roofing felt
0.95
Ice
0.98
Iron (forged), blunt
0.9
Iron, oxidized
0.5 to 0.9
Iron, rusted
0.5 to 0.7
Enamel varnish, black
0.95
Earth
0.92 to 0.96
Paint (not alkaline)
0.90 to 0.95
Paint (non-metal)
0.95
Gypsum
0.60 to 0.95
Glass, pane
0.85 to 0.95
Rubber
0.92 to 0.95
