P
Temperature
Temperature
Compensation
OF & GN
MLX90308
OFTC4
T3
T2
T1
0
3FFh
i1
i2
i3
i4
GNTC4
GNTC3
GNTC2
GNTC1
OFTC1
OFTC2
OFTC3
1 Gap
Application's temperature
range
Figure 9, Temperature Compensation
The first temperature gap is slightly different than the other three. The compensation is based on
the temperature difference between the current temp and the T1 point (the upper end of the gap).
The other gaps use the lower end of the gap to measure the temperature difference. For instance
in the second gap, the temperature difference is current temperature minus T1. This difference
has to be accounted for in the compensation procedure.
Temperature Points
The temperature points T1, T2 and T3 are defined by the user to differentiate between the four
possible temperature compensation ranges. The low endpoint T0 is defined as the minimum
digitized filtered temperature value, zero. This means that the coefficients for the first gap,
OFTC1 and GNTC1, will apply to the signal until the digitized filtered temperature reaches zero.
The high endpoint T4 is defined as the maximum digitized filtered temperature value, 1023
10
.
This means that the coefficients for the last gap, OFTC4 and GNTC4 will apply to the signal
from the T3 point and up until the digitized filtered temperature reaches its maximum, 1023
10
.
When defining these points, the number that is used is simply copied from the ‘Temp Value’ box
at the desired temperature (contents of ram locations 58 and 59).
Temperature Gaps
There are four temperature gaps possible
with the MLX90308. The gaps are defined
with respect to the filtered digitized
temperature value, displayed in the ‘Temp
Value’ box (saved in RAM locations 58 and
59). The first temperature gap is always
bound at the low end by a digitized
temperature value of zero. The fourth
temperature gap is bound at the high end by
a digitized temperature value of 1023
10
(3FF
hex
).
Whenever fewer than four gaps are used, the
last gap should have an upper bound of
1023
10
. This is to ensure that if the
temperature exceeds the last point it won’t
enter into an undefined temperature gap.
MLX90308CCC & MLX90314AB Software Users Manual
Rev 2.0
15
11/28/01