IR contactless thermometers are needed for medical applications to monitor an individual’s body temperature before entering any public place. Depending on the target market and application, the thermal range to be monitored, as well as the required accuracy, may differ significantly. This is especially the case when comparing thermometers used in a medical environment versus those used in industrial applications. This reference design takes into account the thermometer’s range of operation, accuracy, power considerations, and display options. The design is one possible use case for designers.

System Benefits

  • The RL78/I1D microcontroller (MCU) has enhanced analog functions, such as operational amplifiers, a 12-bit A/D converter and window comparators. The MCU also supports very low power operation (124µA at 1MHz ) and a high-speed 4µs wake up.
  • As another option for the design, the RL78/I1B MCU can be used if various enhanced analog functions like a 24-bit Delta-Sigma (ΔΣ) A/D converter are required.
  • The ISL9205 battery charger operates as a pulse charger, where the charge current is determined by the current limit of the AC adapter during the constant current phase. The ISL9205 battery charger operates in a linear mode during the constant voltage phase in both adapter cases.
System Block Diagram

Simplified Contactless Thermometer

Winning Combinations

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