Digital thermometer DS18B20


Just wanted to ask what is inside DS18B20. Is it thermistor, thermocouple or what? Every datasheet mentions that it is digital thermometer but none says what does it measure the temperature with specifically.

Link to datasheet


Probably neither, exactly. Its a small, low-power processor chip, with a circuit designed into it which is temperature sensitive. That circuit probably isn't very linear with respect to temperature, so the chip will use a calculation or look-up table to correct for that after it digitises the reading.


There is an ADC converter in it that gradually gets more bits. I expect it does some oversampling to get the accuracy as the specs states that the waiting time doubles for every extra bit:

(from the head) 12 bit 750 msec 11 bit 375 msec 10 bit 190 msec 9 bit 95 msec

I expect it is a 10 bit ADC that takes ~95 msec for a sample, and for every bit more than 9 it doubles the samples and then shift the result to the format it exports.

It's probably a diode on the die inside that measures the temperature.

I wrote about that to Maxim Integrated. They said it is a PN junction diode.

Its a combination of a bandgap reference voltage of some form and a laser-trimmed sensing pn junction, then analog electronics to amplify the voltage against the reference, then an integrating ADC to convert to digital. At a guess. Google "ideal diode equation" and "bandgap reference". The stuff in the datasheet about "direct to digital temperature sensor" is marketing speak for an analog sensor and an ADC on the same chip.