MLX90614_15 Datasheet, PDF (33/51 Pages) Melexis Microelectronic Systems – Single and Dual Zone Infra Red Thermometer in TO-39

MLX90614 family
Single and Dual Zone
Infra Red Thermometer in TO-39
10.1.2 Medical accuracy
A version of the MLX90614 with accuracy suited for medical applications is available. The accuracy in
the range Ta 16°C…40°C and To 22°C…40°C is shown in diagram below. The accuracy for the rest of the
temperature ranges is the same as in previous diagram. Medical accuracy specification is only available for the
MLX90614Dxx versions.
To, °C
40
± 0.3°C
38
± 0.2°C
36
30
± 0.3°C
22
Ta, °C
20
10
20
30
40
Figure 23: Accuracy of MLX90614DAA (Ta, To) for medical applications.
Accuracy of the MLX90614DCC, DCH and DCI for VDD = 3V (see paragraph 10.1.3)
Versions MLX90614ESF-DCC, -DCH and -DCI comply with ASTM standard section 5.4 (Designation:
E1965 – 98 (Re-approved 2009) - Standard Specification for Infrared Thermometers for Intermittent
Determination of Patient Temperature
It is very important for the application design to understand that the accuracy specified in Figure 22 and
Figure 23 are only guaranteed when the sensor is in thermal equilibrium and under isothermal conditions (there
are no temperature differences across the sensor package). The accuracy of the thermometer can be
influenced by temperature differences in the package induced by causes like (among others): Hot electronics
(heaters / coolers) behind or beside the sensor or when the measured object is so close to the sensor that
heats the thermometer package.
This effect is especially relevant for thermometers with a small Field Of View (FOV) like the xxC and
xxF as the energy received by the sensor from the object is reduced. Therefore, Melexis has introduced the
xCx version of the MLX90614. In these MLX90614xCx, the thermal gradients are measured internally and the
measured temperature is compensated for them. In this way, the MLX90614xCx is much less sensitive to
thermal gradients induced from outside, but the effect is not totally eliminated. It is therefore important to avoid
introducing strong heat sources close to the sensor or to shield the sensor from them.
NOTE: In order to have the highest possible signal and the best performance a higher gain of the
amplifier is selected for MLX90614DCx type of devices. This eventually would limit the maximum object
temperature (due to overload of the ADC) to about 200°C.
10.1.3 Temperature reading dependence on V_DD
In case of medical applications where high accuracy is required and the supply is provided by means of
a battery, a compensation of temperature readings from VDD dependence should be done by the
microcontroller. The dependence is very repeatable and compensation can easily be implemented. As this
3901090614
Rev 009
Page 33 of 52
Data Sheet
June 29, 2015