How does it work?
I've one Temperature to 0-5VDC converter, which convert the temperature sensing from PT100, and convert it to voltage, which supply the power to LED accordingly.
The number array is made of standard 3mm LED,the more leds you use, the more connections and labor time will be required.
+/- polars is parallelly connected.
here 3mm stainless probe pt100 sensor is selected, it response very fast. the led is lit up as the lighter start to heat the sensor probe. see sensor wiring picture.