ON/OFF temperature control (with thermistor and heated body models)

A thermistor NTCLE100 triggers off a comparator , cutting off heating when a certain temperature is reached and switches it on again under a certain treshold (hysteresis) The response time is modelled by a transfer function (Therm. Resp ) with a response time of 15 s. The surrounding ambient temperature is modeled via tempgen1. We see the influence of the ambient temperature on the heating cycle.. When the ambient temperature goes under a certain threshold,the heating duty cycle is 100% and the target temperature cannot be sustained anymore. The user can select a different value for the hysteresis resistor (r10) and see the influence on the overshoot. The target temperature can be adjusted via the DC value of the temperature generator tempgen6 (for the purpose of this example 60 or 70°C: the thermistor element u150 is for simulation only and produces the set target resistance for the comparator) . The tolerance on R25 of the real sensing element u151 can be selected (by default: nominal, choice can be made at +/-2%,+/-3% or +/-5%). The offset between steady temperature and set temperature changes accordingly.

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alain stas

Joined December 10, 2018
Design added Wednesday, March 20, 2019 | 11:57 pm PDT