Data Sheet

MLX90640 32x24 IR array
Datasheet
Page 45 of 60
REVISION 11 – 3 AUGUST 2018
11.2.2.9.1.
11.2.2.9.1.11.2.2.9.1.
11.2.2.9.1. C
CC
Calculations
alculationsalculations
alculations for extended temperature ranges
for extended temperature rangesfor extended temperature ranges
for extended temperature ranges
In order to extent the object temperature range and get the best possible accuracy an additional calculation cycle is needed.
We can identify 4 object temperature ranges (each temperature range has its own so called Corner Temperature – CT which
is the temperature at which the range starts):
- Object temperature range 1 = -40°C … 0°C (Corner temperature for this range is -40°C and cannot be changed)
- Object temperature range 2 = 0°C … CT3°C (Corner temperature for this range is 0°C and cannot be changed)
- Object temperature range 3 = CT3°C … CT4°C
- Object temperature range 4 = CT4°C …
In order to be able to carry out temperature calculation for the ranges outside of temperature range 2 (To = 0°C…CT3)
an additional parameters are needed and must be extracted from the device EEPROM. Those parameters are:
- So called corner temperature (CTx) i.e. the value of temperature at the beginning of the range. Please
note that the corner temperatures for range 1 is fixed to -40°C and corner temperatures for range 2 is
fixed to 0°C while CT3 and CT4 are adjustable
- Sensitivity slope for each range – KsTo
x
- )
P
&
pÖ
'
calculated in 11.2.2.9
11.2.2.9.1.1. Restoring corner temperatures
The information regarding corner temperatures is stored into device EEPROM and is restored as follows:
¡ZYG


‰



%
!
NNº

%
!!!×=
=)


‰

‰

q
!¡ZYG
NNº‰

q
!N!N! ×=
=)


‰

‰


!¡ZYG<=)
NNº‰


!< N!< N!< ×=
Or we can construct the temperatures for the ranges as follows:
CT1=-40°C < Range 1 > CT2=0°C < Range 2 > CT3=160°C < Range 3 > CT4=320°C < Range 4
11.2.2.9.1.2. Restoring the sensitivity slope for each range
X
?]
a0bc
 has been extracted in 11.1.10
X
?]

X
?]MKK

;r
.d
a0bc



¸
¼NN N
Where:
X
?]MKK


¢

‰‰ºº‰‰º (signed)
If X
?]MKK
 X
?]MKK
X
?]MKK
  
X
?](

X
?](MKK

;r
.d
a0bc



¸
¼NN N
Where:
X
?](MKK


¤

‰‰ºº‰‰º (signed)