The next two slides show simple simulations involving RTDs, both making use of Vishay’s PTS series of platinum thin film SMD temperature sensor components. This simulation is performed in LTspice® and shows a temperature control of an oven whose temperature (Tsystem) is controlled around 40°C by a 1 KΩ Vishay PTS RTD with the help of an AC heater controlled by a Vishay VOT8125 optotriac. On the left of the schematic is a sensing Wheatstone bridge with the 1 KΩ PTS RTD, whose temperature input is directly provided by the thermal circuit modeling the oven. The response time of the PTS sensor is modeled by a simple RC circuit. The multiple curves on the graph on the bottom right show the dynamic temperature control around 40°C, with a well-defined hysteresis (for a Monte Carlo analysis) where all the tolerances of the passive elements are explored. Notice how the temperature in degrees Celsius is now indirectly represented in LTspice by using a manipulation of a voltage unit, dividing it by a factor of 1°C / 1 V.