A portable, low profile electric radiant heater has an elongated heating element. A plurality of thermistors are disposed proximate to and along the length of the elongated heating element, spaced at substantially equal intervals. A microcontroller switches a reference resistor in series with a charging capacitor to determine a reference timer value. The microcontroller switches banks of multiple thermistors in series with the charging capacitor to determine associated timer values. The microcontroller calculates thermistor resistance values using the reference timer, reference resistor, and thermistor timer values. A lookup table is employed to determine a temperature value associated with the thermistor resistance value. This serves as the sensed temperature of the associated bank of thermistors. A plurality of tip-over switches are provided. One tip-over switch is disposed between the microcontroller and the heating element. Another tip-over switch is disposed between the microcontroller and the banks of temperature sensing thermistors.