MLX90621 datasheet(17/44 Pages) MELEXIS

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MLX90621

16x4 IR array

Datasheet

39001090621

Page 17 of 44

Datasheet IR16x4

Rev 3.0

15 September 2016

Calculation of To

7.3.3.

Following formula is used to calculate the temperature seen by specific pixel in the matrix:

Q(J,•)

x y€c(r,•)nefdb‚ƒ„`bi

…†o‡ˆ(r,•)∗(3E_‰v∗6UD.3M)V)h(r,•)4 /_v

0 273.15,8° =

Where: 9ŠL(J,•)_FQ(PO‹)z2OT istheparasiticfreeIRcompensatedsignalascalculatedin7.3.3.1

Œ•GŽ•(J,•) isthecompensatedsensitivitycoefficientforeachpixel

1•N isthecompensationfactorforthesensitivity–forBABandBAD,1•N 0, resultinginasimplified

formula

/_v ( / 4 273.15)N where / is the ambient temperature calculated in 7.3.2

S(J,•) 1 4 ∗

5Œ‘ ’“(,&)3 ∗9# (,&) ” •– •— 4 Œ‘ ’“(,&)4 ∗ 14

Calculating VIR(I,j)_COMPENSATED

7.3.3.1

Offset compensation

9ŠL(J,•)eqq‰t˜no‡ˆtp‰™˜tš 9ŠL(J,•) 0› J(J,•) 4 J(J,•) ∗ ( / 0 /R)œ

Where: 9ŠL(J,•)isanindividualpixelIR_datareadout(RAMread)

J(J,•) is an individual pixel offset restored from the EEPROM using the following formula:

J(J,•)

z†o‡‡opV∆zr(r,•)∗6∆„r‰†™žt

6jmnopqrscts8u:v=

•GŽŽGH is the minimum offset value stored in the EEPROM at addresses 0xD0 and

0xD1 as 2’s complement value

∆ J isthedifferencebetweentheindividualoffsetandtheminimumvalue.Itisstoredin

the EEPROM as unsigned values.

∆ J‰†™žt isthescalingcoefficientforthe∆ J valuesandisstoredintheEEPROMat

address 0xD9[7:4] as an unsigned value

J(J,•) is an individual pixel offset slope coefficient

J(J,•)

*r(r,•)bbdcef

6Ÿr‰†™žt∗6jmnopqrscts8u:v=

J(J,•)bbdcef is the value stored in EEPROM as two’s complements

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