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TMP007AIYZFT データシートの表示(PDF) - Texas Instruments

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TMP007AIYZFT Infrared Thermopile Sensor with Integrated Math Engine TI
Texas Instruments TI
TMP007AIYZFT Datasheet PDF : 55 Pages
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TMP007
SBOS685C – APRIL 2014 – REVISED JULY 2015
www.ti.com
Feature Description (continued)
7.3.4 Object Temperature Calculation
The TMP007 generates a sensor voltage, VSensor, in register 00h that is related to the energy radiated by the
object. For an ideal situation, the Stefan-Boltzman law relates the energy radiated by an object to its temperature
by the relationship shown in Equation 5:
EnergyRad = esTO4BJ
where
σ = Stefan-Boltzman constant = 5.67 × 10-12 W/(cm2K4)
ε = Emissivity, 0 < ε < 1, an object dependent factor, ε = 1 for a perfect black body
(5)
A similar relationship holds for the sensing element itself that radiates heat at a rate determined by TDIE. The net
energy absorbed by the sensor is then given by the energy absorbed from the object minus the energy radiated
by the sensor, as shown in Equation 6:
( ) VSENSOR µ EABSORBED - ERADIATED = es TO4BJ - TD4IE
(6)
In an ideal situation, the sensor voltage relates to object temperature as shown in Equation 7:
TOBJ = 4 TD4IE + VSENSOR
es
(7)
TOBJ
=
4
TD4IE
+
æ
ççè
ƒ
{VOBJ
S
}ö
÷÷ø
where
S is a system-dependent parameter incorporating the object emissivity (ε), FOV, and sensor characteristics.
The parameters S0, A1, and A2 are used in determining S.
f(VOBJ) is a function that compensates for heat flow other than radiation, such as convection and conduction,
from nearby objects. The parameters B0, B1, and B2 are used to tune this function to a particular system and
environment.
(8)
The coefficients affect object temperature measurement as described in Table 1.
COEFFICIENT
S0
A1, A2
C2
B0, B1, B2
Table 1. Calibration Coefficient Definitions
PURPOSE
FOV and emissivity of object
Device properties
Device properties
Corrects for energy sources
CALIBRATION
Application and object
dependent
Factory set
Factory set
Environment dependent
COMMENT
Default values based on black body with ε = 0.95, and
110° FOV
Default values based on typical sensor characteristics
Default values based on typical sensor characteristics
Calibrate in end-application environment
14
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