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Image of Vishay's Simulation of Temperature Reading with ADC Image of Vishay's NTC-PTC Temperature Reading Simulation

The first example of a more elaborate application is the simulation in LTspice® XVII of temperature sensing by Vishay NTC thermistor part number NTCLE317E4103SBA. This product is what is known as a two-point sensor, meaning it has an interchangeable accuracy of ±0.5°C between 25°C and 85°C and ±1°C maximum outside (to the operating temperature limits of -40°C to +150°C). The voltage produced by a thermistor-based voltage divider is filtered, sampled, and converted into a digital signal and then reconverted into temperature with the help of the Steinhart and Hart formulas which define an NTC thermistor’s resistance-to-temperature relationship. The deviation between the readout and the real temperature is then computed in time and plotted in function of the real temperature. The tolerance on the thermistor is modeled based on a Monte Carlo distribution. It is obvious on the presented graph that the modeling (green curves) falls within the specification limits (blue and red curves). If more runs are performed, the whole specification will be covered. The small noise appearing on each of the green curves is the quantization noise.

PTM Published on: 2021-01-05