Lighting Industry Technical Note
Heitronics has been very active within the lighting industry
over the past 20 years. Major users of our products include
Osram-Sylvania, Philips and General Electric. Many of the
features that are now standard in the Heitronics product
line are a result of being active in this area.
Why do Heitronics products meet the requirements found
within the Lighting Industry?
1) The detector used by Heitronics is a Heitronics design.
It is a Lithium Tantalate pyroelectric crystal
which does not drift in its detectivity.
Benefit: An inherently stable pyrometer.
There is no need for an automatic internal correction feature
which is offered by a reputable competitor.
KT19 long term stability is better than 0.0001( reading
in K) per month.
2) The pyroelectric detector requires the challenge of
chopping the radiation signal in order to make the detector
work. Heitronics has used chopper motors in every commercial
instrument since the first pyrometer design in 1959. The
chopper motor used in KT19 series is a Heitronics design
which offers an MTBF of 9 years.
Benefit: The resulting use of AC electronic
circuits which are more stable than DC circuits. Accuracy
is ± (0.5°C + 0.007( target temp. - housing temp.)).
3) Pyroelectric based pyrometers are capable of responding
faster than competitive thermopile based pyrometers. (The
Heitronics response time definition is the time required
to respond to 90% of a step change in temperature. Multiply
this response time by x 1.5 to approximate the 99% value.)
Benefit: KT19 series has adjustable response
time to as fast as 30ms.
4) The availability of 35 standard lenses, 10 standard
possibilities of positioning the lenses out in front of
the detector and 4 different detector aperture sizes provides
close to a thousand fixed focus options. Combine the focus
options with high quality lenses, a very rugged way of precisely
fixing the lens in front of the detector and the result
is a very high distance to target size ratio. (Heitronics'
definition of spot size is for the area where 95% of the
total radiant signal comes from.)
Benefit: Distance to target size ratios
for the 4.9 to 5.5 microns spectral band can be delivered
as high as 220:1, for the 400 to 2500°C temperature
range which allows viewing small targets at a safe distance
from heat, silica dust and moving machinery.
5) KT19 series offers three ways in which to help aim the
instrument; through the lens visual sighting, laser illumination
of the target center or LED illumination of the target area.
The precise way in which Heitronics' production staff aligns
the combination of visual, internal light source and infrared
target area ensures the coincidence of these three parameters.
Benefit: The assurance that when careful
aiming is done on small and specific target areas, the infrared
measurement will be made from where it is wanted.
6) KT19 series is 1990's technology using the latest available
surface mounted device components and microprocessors.
Benefits: Complete programmability is
available via the rear keyboard or via a bi-directional
digital interface. A digital display is incorporated on
the instrument's rear face. All electronics are built within
the one compact sensor housing which saves space and installation
expense.
7) The suggested 4.9 to 5.5 microns spectral response of
KT19.42 corresponds with the glass and quartz absorption
band. Viewing through flames or making the temperature measurement
of the glass surface while under the direct presence of
flame is made with a minimum amount of influence. We suggest
to use an emissivity setting of 0.96 for this spectral response.
Many other spectral responses are available for applications
including low temperature glass measurements and metal surfaces.
Benefits: Use of Heitronics pyrometers
is possible virtually anywhere within the lamp plant.
8) KT19 includes as standard features, an external secondary
temperature sensor input or can be programmed by a given
value for compensating for the contribution of a high temperature
background as seen via the 4% reflection off of the glass
target area.
Benefit: Measurement of glass surfaces
within lehr's can be made while correcting for the contribution
of radiation from within the lehr.
9) An effective air purge fitting design ensures that the
lens can remain clean when the recommended 5 psi of nitrogen
is connected.
Benefit: The major cause for an "apparent"
change in instrument calibration can be eliminated by keeping
the lens clean.
10) KT19 housing design is water-tight, dust-tight and
shielded from electromagnetic interferences. It is available
as standard to withstand up to 60°C ambients and perform
to all published specifications. It is also available in
a coolable housing version for handling up to 150°C
ambients.
Benefit: It survives the conditions that
the lighting industry presents.
Selected instrument specifications which have been applied
to Lighting Industry applications:
Heitronics Model KT19.42, 4.9 to 5.5 microns spectral
response
Use: Surface measurement of quartz and
glass during lamp fabrication and research
Features: Fast response time ( 30ms );
high optical resolution ( 220:1 distance to target ratio,
i.e.: 1mm dia. @ 203mm distance; 2.5mm dia.@ 550mm distance
); wide temperature range 150 to 1600°C or 400 to 2500°C;
long term stability better than 0.0001 (reading in K ) per
month; through the lens sighting, laser sighting or LED
sighting; linearized analog outputs and bi-directional digital
interface
Benefits: View through flame, measure
clear glass*/quartz surface to depth of 0.05mm @ 1400°C;
proven to repeat measurements of 2100°C with 30ms response
time to ±6°; high repeatability allows output
signal to be put into a control loop
Heitronics Model KT19.43, 7.5 to 8.2 microns spectral
response
Use: surface measurement of quartz and
glass during lamp fabrication and research
Features: Fast response time ( 30ms );
wide temperature range 200 to 1200°C; long term stability
better than 0.0001 (reading in K) per month; through the
lens sighting and/or LED or laser sighting; linearized analog
outputs and bi-directional communications
Benefits: Measure clear glass*/quartz
surface to depth of 0.01 mm @ 700°C; high repeatability
allows output signal to be put into a control loop, emissivity
= 0.98 for this spectral response
Heitronics Model KT81R, ratio of two wavebands between
0.7 to 1.2 microns
Use: Measurement of tungsten and molybdenum
for research and production
Features: Ratio of two wavelength technique
permits the measurement of metals with low and potentially
changing emissivity; through the lens sighting, adjustable
aperture to block radiation from unwanted surrounding sources,
controlled detector temperature plus chopped radiation technique
provides highest degree of measurement stability while reducing
the dependency of requiring a greybody target, linearized
analog output direct from sensor, temperature range, cover
700 to 3600°C
Benefits: Target need not fill the field
of view ( 50 micron tungsten wire @ 1000°C can be measured
with focus of 10mm diameter ), views through quartz windows
found on hydrogen sintering furnaces; target can wander
within the field of view but because of the chopped radiation
technique, if the target wanders out of the field of view,
a high reading will result for a duration equal to the response
time; additional signal conditioning hardware available
for handling targets which wander out of the field of view
Heitronics Model KT81S, 0.7 to 1.2 microns spectral response
Use: Measurement of tungsten and molybdenum
for filament research
Features: High optical resolution for
viewing 0.005 inch diameter @ 4 1/8 inch distance, spectral
response permits viewing through glass and quartz envelopes;
10 millisecond response time, temperature ranges cover 1100
to 3450°C; calibration accuracy ±3°C plus
0.5% of target temperature; linearized analog output direct
from sensor
Benefits: Measurements made on an electronic
basis as compared to a human basis as previously found on
disappearing filament optical pyrometers; views through
quartz and glass envelopes
* Reference: Theory and
Practice of Radiation Thermometry, DeWitt and Nutter, 1989
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