This is a simulation in LTspice XVII (presently offered by ADI) of a project for oil temperature sensor for temperatures going from 50°C up to 185°C. The base element is a Vishay thermistor NTCLE350 (PEEK insulated leaded NiFe 0.2 mm wire 30Kohms +/-1%) whole LTspice modeling can be downloaded from the attachments to this projects. The particularity of this simulation is that all tolerances of the NTC thermistor and all the other passive elements are modeled according to a simple Monte Carlo Function. The circuit is presented in the following picture:
The simulation of the output voltage in function of the temperature TEMP gives the following graph
It is then possible with some spice directives to determine the accuacyy of the Vout measurement : at 185 °C, Vout is equal to 10.06 V nominally. Introducing tolerances for the circuit elements, we can the compute in which temperature span the Vout voltage will cross 10.06V. the spice error log file allows to visulaize this span which will swing between 183 and 187°C, thus 185°C +/-2°C, values relatively near the specification
On of the advantage of the simulation is that the user can program other tolerances at will and visualize in no time the results. Here is the results with dR25 =5% and dRfix=1%
In the spice error log file, the temperature span corresponding a real 185°C temperature, can be evaluated around 182°C-188°C. The user can thus evaluate if the tolerance decreasing (price increase) is worth the value of the improved accuracy.