Temperature sensor one wire or voltage level?

Discussion in 'General Electronics Chat' started by spinnaker, Dec 18, 2010.

  1. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
    I am considering building a temperature logger. I have been looking at various temperature sensors. Among the IC versions there is one wire and a type that just gives a voltage level.

    I would think that the advantage of one wire is that you don't need to worry about the sensitivity of your ADC though they are a little more expensive.

    Any other advantages? I would think the voltage level versions rely on the accuracy of your voltage reference for the accuracy of the temperature.

    I can see where the 1 wire versions are more complicated to interface but probably more interesting.

    Do the one wire versions compensate for variations in the supply voltages (i.e. reference voltage)?
  2. Jaguarjoe

    Active Member

    Apr 7, 2010
    An inexpensive Maxim/Dallas DS18B20 12 bit sensor has 0.5C accuracy and simple one wire hookup. A cheap and easy Picaxe uP has a one wire command that makes using and programming trivial. Free samples too.

  3. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    I use the ones with the 1 wire or an SPI interface built in. Saves a bit of code on the processor, as well as an ADC port time, allowing for faster response to other sensors.

    Accuracy is the same or better with the digital output compared to the analog out going to uC's A/D and software calibration of the voltage read.

    If you want degF and have a degC, the 9/5+32 is a quick calculation as well, sometimes one is cheaper than the other is the only reason I mention this.
  4. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009
    Thanks everyone for the responses.

    I do not understand Alberto. Everything I have read says that doing ADC with your VDD as a reference is fine but if you want real accuracy, then a more accurate voltage reference is needed.
    How does that make a difference here?
  5. spinnaker

    Thread Starter AAC Fanatic!

    Oct 29, 2009

    Ah got it! I see. It all makes sense now. Thanks.