MLX90621 datasheet(14/44 Pages) MELEXIS

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MLX90621

16x4 IR array

Datasheet

39001090621

Page 14 of 44

Datasheet IR16x4

Rev 3.0

15 September 2016

Calculation

7.3.

Calculation of absolute chip temperature Ta (sensor temperature)

7.3.1.

The output signal of the IR sensors is relative to the cold junction temperature. That is why we need to know the

temperature of the die in order to be able to calculate the object temperature ‘seen’ by each pixel.

The Ta can be calculated using the formula:

/ 0123 4 5123

0 4126892:(25)0

_ =

2126

425,8>=

Constants

)

(

and

are stored in EEPROM at following addresses as two’s complement values:

EEPROM address

Cell name

Stored as

Parameter

0xDA

VTH_L

2’s complement

VTH0 of absolute temperature sensor

0xDB

VTH_H

0xDC

KT1_L

2’s complement

KT1 of absolute temperature sensor

0xDD

KT1_H

0xDE

KT2_L

2’s complement

KT2 of absolute temperature sensor

0xDF

KT2_H

0xD2

KT_scale

unsigned

[7:4] – KT1_scale

[3:0] – KT2_scale

Table 5 EEPROM parameters for Ta calculations

92:(25) 256 ∗92:_: 4 92:_.

# 92:(25) @ 32767 → 92:(25) 92:(25) 0 65536

92:(25)

2DEFGHIJKL-K8M:N=

123 256 ∗ 123_: 4123_.

123 @ 32767 → 123 123 0 65536

123

2OOLPQ(RST68U:N= ∗ 2DEFGHIJKL-K8M:N=

126 256 ∗ 126_: 4126_.

126 @ 32767 → 126 126 0 65536

126

2OOLPQ(RST68D:R=V3R ∗ 2DEFGHIJKL-K8M:N=

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