Hi,
I have the exact same thing. When you start all is normal, but as soon as you touch the sensor it goes up to the unrealistic high values and won't come down again. When you unplug the Arduino and plug it in again, the sensor returns the correct value again and it all starts over again..
Sensor value: 147, Volts: 0.72, Degrees C: 21.78
Sensor value: 146, Volts: 0.71, Degrees C: 21.29
Sensor value: 147, Volts: 0.72, Degrees C: 21.78
Sensor value: 147, Volts: 0.72, Degrees C: 21.78
Sensor value: 147, Volts: 0.72, Degrees C: 21.78
Sensor value: 146, Volts: 0.71, Degrees C: 21.29
Sensor value: 146, Volts: 0.71, Degrees C: 21.29
Sensor value: 146, Volts: 0.71, Degrees C: 21.29
Sensor value: 146, Volts: 0.71, Degrees C: 21.29
Sensor value: 146, Volts: 0.71, Degrees C: 21.29
Sensor value: 146, Volts: 0.71, Degrees C: 21.29
Sensor value: 149, Volts: 0.73, Degrees C: 22.75
Sensor value: 172, Volts: 0.84, Degrees C: 33.98
Sensor value: 208, Volts: 1.02, Degrees C: 51.56
Sensor value: 208, Volts: 1.02, Degrees C: 51.56
Sensor value: 201, Volts: 0.98, Degrees C: 48.14
Sensor value: 201, Volts: 0.98, Degrees C: 48.14
Sensor value: 201, Volts: 0.98, Degrees C: 48.14
Sensor value: 200, Volts: 0.98, Degrees C: 47.66
Sensor value: 201, Volts: 0.98, Degrees C: 48.14
Sensor value: 200, Volts: 0.98, Degrees C: 47.66
Sensor value: 200, Volts: 0.98, Degrees C: 47.66
Sensor value: 200, Volts: 0.98, Degrees C: 47.66
Sensor value: 199, Volts: 0.97, Degrees C: 47.17
Sensor value: 200, Volts: 0.98, Degrees C: 47.66
Sensor value: 200, Volts: 0.98, Degrees C: 47.66
Sensor value: 200, Volts: 0.98, Degrees C: 47.66
Sensor value: 199, Volts: 0.97, Degrees C: 47.17
Sensor value: 199, Volts: 0.97, Degrees C: 47.17
Sensor value: 198, Volts: 0.97, Degrees C: 46.68
Sensor value: 198, Volts: 0.97, Degrees C: 46.68
Sensor value: 199, Volts: 0.97, Degrees C: 47.17
Sensor value: 199, Volts: 0.97, Degrees C: 47.17
Sensor value: 199, Volts: 0.97, Degrees C: 47.17
Sensor value: 199, Volts: 0.97, Degrees C: 47.17