TPMI PerkinElmer Optoelectronics, TPMI Datasheet - Page 4

• Manufacturer Part Number: TPMI
• Description: Thermopile Sensor Module
• Manufacturer: PerkinElmer Optoelectronics

TPMI™ -
Ambient
The thermopile sensor generates a voltage U
proportional to the incident net radiation P
with S = sensitivity, K = instrumentation factor containing
the Stefan-Boltzmann constant and the view angle,
ε = emission factor.
The equation shows that for a fixed ambient temperature,
the thermopile output voltage U
As also seen from the equation, the output signal will vary
when the ambient temperature changes and, therefore,
the TPMI will need to compensate this effect. Because the
ASIC has good thermal contact with the thermopile
sensor, it measures exactly the ambient temperature with
its integrated linear temperature sensor. In order to
achieve a best fit to the thermopile T
linear temperature signal will be further processed into a
polynomial behavior, which approximates the
characteristic to the required T
temperature range.
Measurement Results and
Ac
In mass production, the TPMI Modules are
calibrated under controlled ambient
conditions. Different black body temperatures
are used for calibration and testing. This
procedure ensures a precise adjustment of
the output curve and an excellent
reproducibility from batch to batch. The
PerkinElmer TPMI is indeed a consumer type
pyrometer head, but due to the sophisticated
adjustment procedures for an device with
100°C range an absolute accuracy of better
than ±2.5 K over the whole ambient
temperature range of 10 to 60°C is
achievable. In fact, an accuracy of ±1 K at
the calibration point is accomplished. For the
TPMI, the achievable measurement accuracy
depends mainly on the measurement range
(higher range induces lower accuracy) and the ambient
temperature span (below 10°C and above 70°C deviations
occur). It has to be noted, however, that under dynamic
conditions, i.e. object or ambient temperature changes,
the specified values might temporarily not be met due to
temperature inhomogeneities over the sensor module.
The curve in Figure 4 shows a typical deviation of the
measured temperature as a function of ambient
temperature variation. For temperatures between 10°C
and 80°C the VTObj output is relatively independent from
TPMI™ -
Ambient
Measurement Results and
Ac
hie
hie
v
v
ab
ab
Thermopile Sensor Module
Thermopile Sensor Module
T
T
le Accurac
le Accurac
emperature Compensation
emperature Compensation
y
y
w w w . p e r k i n e l m e r . c o m / o p t o e l e c t r o n i c s
4
TP
behavior over a large
is proportional to T
4
characteristics, the
rad
With Integrated Signal Pr
With Integrated Signal Pr
:
TP
, which is
Figure 4
obj
4
.
This voltage is added to the thermopile signal in the
compensation stage. It has to be noted that the ambient
temperature compensation needs to be adapted to each
individual application. In particular it is determined by:
• The viewing angle, which depends on the optics, i.e. the
• The emission factor, which is dependent of the material
• The sensitivity of the thermopile chip and its temperature
• The total temperature range to be measured
These factors need to be determined first in order to
assess the needs of the customer. PerkinElmer can
provide assistance in finding the optimum conditions for
an individual mass production part.
changes of T
becomes nonlinear related to T
a decreased approximation of the T
temperature measurement. The same effect occurs at
ambient temperatures below 10°C.
aperture, the optical lens or mirror,
and surface of the measured object,
coefficient, which should be as small as possible (note:
PerkinElmer thermopiles are designed to have an
extremely small temperature coefficient),
ocessing
ocessing
ambient
temperature variation. Note the wide interval ranging
Typical measurement error as a result of ambient
from 10°C to 80°C, where the object temperature
. Above 80°C the VTObj characteristics
ambient
deviation is smaller than 0.5°C.
4
, which is caused by
by the ambient
Page 4