OBJ

30 nW

T

140 mK

213 nW/K

'

|





3

3

OUT

8

OBJ B OBJ

det

OBJ

OBJ

3

0

V

nW

NEP

T

A

1 cos

T

213

T

R

K

H

V

T

'

§

·



'

'

¨

¸

©

¹

.

rms noise

OBJ

OUT

Sensor

0.25 9

T

110 mK

V

2 3 9.

'

|

'

.

SENSOR

OBJ



'

V

2 3

T

K





K





cos

3

3

8

OUT

OBJ B OBJ

det

0

OBJ

3

V

T

A

1

R

T

H

V

T

'



'

.

2

2

2r

cos

0 800

4r

D

T







4

4

3

SENSOR

OBJ B

OBJ

DIE

det

0

2

V

=

T

T

A

(1

cos

)R

3

H

V

T





TMP006, TMP006B

www.ti.com

SBOS518E – MAY 2011 – REVISED APRIL 2015

Using the device-specific radiation transfer expression and R0, the detector response is shown in Equation 14:

where

•

•

B is the Stefan-Boltzmann constant (5.67 × 10

•

•

•

•

θ is the half-angle subtended by the object as viewed from the detector.

•

(14)

The value of cos

θ is shown in Equation 15:

where

•

r is the distance between the detector and the object (10 mm).

•

D is the diameter of the object (15 mm).

(15)

Differentiating with respect to object temperature, a small change in temperature creates a small change in the

measured voltage given by Equation 16:

(16)

Substituting values for the parameters yields Equation 17:

(17)

shown in Equation 18:

(18)

The peak-to-peak noise is approximately six times the rms noise; therefore, estimate an accuracy of

approximately ±0.33°C.

This estimate can also be made using the noise-equivalent power (NEP), noting that NEP is the ratio of noise to

responsivity, as shown in Equation 19:

(19)

Assuming the system is sensor-noise limited, the NEP is ~30 nW at 25°C, as shown in Equation 20:

(20)

Again, the peak-to-peak noise is approximately 6X the rms noise; therefore estimate an accuracy of

approximately ±0.42°C.

The different results from these two techniques is because of estimated values used for some parameters. The

purpose of these techniques is not to obtain exact answers, but rather to quickly estimate the feasibility of a

system implementation based on basic system parameters. These examples are intended only as guidelines; the

specific values for the parameters depend on the specific system details.

Copyright © 2011–2015, Texas Instruments Incorporated

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