Optris CT P3 User Manual
innovative infrared technology
Production
Quality Assurance
Research & Development
Test & Measurement
NON-CONTACT
TEMPERATURE MEASUREMENT
PLASTICS INDUSTRY
Plastics industry
Wavelength in µm
2 4 6 8 10 12 14 16
ENGINEERING / PHYSICS
Inuence from the surroundings
The illustration shows that the transmissivity of air strongly
depends on the wavelength. Strong attening alternates with
areas of high transmissivity – the so-called atmospheric windows.
The transmissivity in the long-wave atmospheric window
(8 – 14 µm) is constantly high whereas there are measurable
extinctions by the atmosphere in the shortwave area, which may
lead to false results. Typical measuring windows are
1.1 – 1.7 µm, 2 – 2.5 µm and 3 – 5 µm.
Additional inuences can arise from heat sources in the
environment of the measuring object. To prevent wrong
measuring results due to increased ambient temperatures,
the infrared thermometer compensates the inuence of ambient
temperatures beforehand (as e.g. when measuring temperatures
of plastic foils in heating areas whereby the walls are hotter than
the measuring objects). A second temperature sensing head
helps to generate accurate measuring results by automatically
compensating the ambient temperatures and a correctly adjusted
emissivity.
Radiation
from
ambient
n
T
Object
amb
ρ
n
T
n
T
amb
obj
= α
ε
τ
Sensor
α = Absorption ρ = Reflectance τ = Transmission ε = Emissivity
Compensating ambient influences
Emissivity and temperature measurement
of plastics
Emissivity is a key factor in the accurate measurement
of temperatures. It depends on various inuences and must
be adjusted according to the application.
100
75
Transmissivity in %
50
25
0
Spectral transmissivity of air (1 m, 32 °C (90 °F), 75 % r. F.)
Dust, smoke and suspended matter in the atmosphere can pollute
the optics and result in false measuring data. Here air purge
collars (which are installed in front of the optics with
compressed air) help to prevent deposition of suspended
matter in front of the optics. Accessories for air and water
cooling support the use of infrared thermometers even in
hazardous surroundings.
Emissivity theoretically depends on the material, its surface
quality, wavelength, the measuring angle and, in some cases,
even the applied measuring conguration.
Plastics with a thickness of > 0.4 mm (0.02 in) and pigmented
lms can be measured very easily in the long-wave IR spectral
range (8-14 µm) with emissivities of ≥ 0.9.
IR Transmission of polyimide foil
Transmission [%]
Wavelength [µm]
Transmission of PE foil
Transmission [%]
2
Wavelength [µm]
The CoolingJacket Advanced enables an
operation within an ambient temperature
of up to 315 °C (599 °)
innovative infrared technology
Line scan with compact infrared camera
for thick plastic lms
Plastics processors produce a wide range of products
of various dimensions, thicknesses, textures, colors
and embossed patterns. Here the manufacturing is
subject to numerous thermal processes which have
to be continually and rigorously checked at various
critical points.
In order to ensure quality, a high level of temperature
homogeneity is required and this is checked at
various stages, including during thermoforming and
in the calender zone, by means of a line scan.
In-depth inspection of preforms during bottle production.
Very thin plastic lms are, however, transparent in this spectral
range, meaning that a temperature measurement is only possible
with the aid of material-specic absorption bands in the IR
spectrum via correspondingly narrow-band sensitive IR sensors.
Polyethylene, polypropylene, nylon und polystyrene, for example,
are IR opaque at 3.43 μm; for polyester, polyurethane, Teon,
FEP and polyamide, in contrast, it is 7.9 μm.
C-H band
3.43 μm
P3 > 50 °C (122 °F)
C-F Ester band
7.95 μm
P7 > 0 °C (32 °F)
Polyethylene (PE) Yes No
Polypropylene (PP) Yes No
Cellophane Ye s No
Polystyrene (PS) Yes No
Fluoroplastic (FEP) No Yes
Polyimide No Yes
When using an infrared camera as a line scanner,
an arbitrary line is selected from the detector array.
In addition to the compact construction and the lower
price, there are two signicant benets: the line to
be scanned can be positioned anywhere using the
software and the user receives a complete IR image
quasi as additional information – these are important
advantages, especially during system setup.
The cameras can accurately measure surface temperatures of moving measurement objects using minimal
apertures. This function is of particular signicance
in the plastics industry, since homogeneity of foil
temperature has a direct impact on the quality of the
nal product. During the production process,
temperatures are measured accordingly at many
points and it is possible to intervene in the process,
when necessary, if there are deviations in setpoint
temperatures.
The optris PI 640, in combination with the 90° lens,
allows for high-resolution line scanning with up to
800 pixels and a maximum scan angle of 111° with
the use of the diagonal dimension.
Acrylic Yes Yes
Polycarbonate Yes Yes
Polyester Yes (>10 μm) Yes
F2F
–C–C–C–C–
Polyethylene
Further information in our infrared basics brochure:
www.optris.com/optris-downloads
CF
3
2
F
n m
FEP
Lines have FOV of
up to 111° for detailed
process analysis.
F
2
111 °
any number of lines
800 Pixel
Up to 125 Hz data recording
of unlimited lines which in turn
produce a thermal image of
any given resolution
3
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