Basic digital thermometer
The described circuit utilizes the ICL7106, a high-accuracy analog-to-digital converter (ADC) designed for voltmeter applications. In this context, the circuit measures temperatures on the Kelvin scale, which is crucial for scientific and industrial applications where absolute temperature readings are required. The theoretical range of the Kelvin scale extends from 0 K to 1999 K, while practical implementations typically operate within a narrower range of 223 K to 473 K.
To ensure that the input voltage levels fall within the common-mode voltage range of the ICL7106, a 26 kΩ resistor is employed. This resistor acts as a current-limiting device, protecting the ADC from potential overvoltage conditions that could occur during operation. The choice of a 26 kΩ resistor is critical as it balances the voltage levels presented to the ADC while maintaining accuracy in the readings.
Additionally, the circuit design allows for the substitution of two general-purpose silicon diodes or an LED in place of the resistor. This flexibility can be advantageous in applications where different components may be more readily available or where specific performance characteristics are desired. Silicon diodes can provide a forward voltage drop that can be utilized for calibration purposes, while an LED may serve as an indicator for operational status.
In summary, this circuit configuration is designed to accurately read temperatures in the Kelvin scale using the ICL7106 ADC, with specific attention to input voltage ranges and component flexibility. The integration of a 26 kΩ resistor ensures that the system operates within safe limits, enhancing the reliability and accuracy of the temperature measurements.The Kelvin scale version reads from 0 to 1999 °K theoretically, and from 223 °K to 473 °K actually The 26 K resistor brings the input within the ICL7106 Vcm range: two general-purpose silicon diodes or an LED may be subsituted.
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