digital temperature sensor

Discussion in 'General Electronics Chat' started by Col, Jun 14, 2012.

  1. Col

    Thread Starter Member

    Apr 19, 2012
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    Hi,

    I'm looking for a digital temperature sensor which has a single wire interface I can use directly to my modulation input of my RF transmitter. I hope to avoid using a processor. I can trade off most things like resolution/accuracy, although I would like to measure 150degrees C.

    I've looked at a few (eg http://www.ti.com/product/tmp141 and http://www.maxim-ic.com/datasheet/index.mvp/id/2794) but these look like they need some configuration input from a master.

    Any idea if this kind of stand alone, single wire digital output thermometer exists?

    Thanks
     
  2. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    and what do you plan to read this digital output with?
    You expect an IC temp sensor to survive 150 deg C? is that absolute max?
    What about thermocouples or RTD?

    I think you need to describe your intended use here.
     
  3. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    You're looking for something like an old school LM35, but 150°C is above the range of this and most devices.

    For that range I would go with a true thermocouple and amplifier such as the Analog Device AD595-AQ.
     
  4. tracecom

    AAC Fanatic!

    Apr 16, 2010
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    The LM35C will operate up to 150°C. It is sometimes called a "one-wire" device even thought it takes three wires; power, ground, and signal. It provides a voltage that is directly proportional to the temperature.

    https://www.national.com/ds/LM/LM35.pdf
     
  5. Col

    Thread Starter Member

    Apr 19, 2012
    44
    2
    my sensor is going into a very nasty environment, which will probably destroy it... so as little as possible should be in the sensor side. At least I will have a power source and an RF transmitter + antenna. I would like a single wire digital bit stream of temperature measurements, which input to the modulation input of my RF transmitter will ASK modulate its RF signal. I will receive this and process on that end.

    Most of the digital '1-wire' interface devices I have found are using a 1 wire bus. This needs a microcontroller to provide commands to the sensor... this is what I want to avoid

    The 150 isnt a deal breaker, I can handle 125... my sensor is expected to die at about about 140

    LM35 is and analogue part... I could handle that if I could connect it with a freerolling ADC requiring no master control.

    This device might work... only a pull up needed to set in active mode http://www.smsc.com/media/Downloads_Public/Data_Sheets/1201_1202.pdf
     
  6. wmodavis

    Well-Known Member

    Oct 23, 2010
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    I have 3-wire 100 Ohm stainless steel encased RTD sensors which are made to withstand harsh environments and withstand much higher temperatures. If the electronics were outside the harsh environment and as little as possible is on the sensor side. However doesn't meet your other requirements.

    Keep digging.
     
  7. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    what about xbee RF modules.. I think they all have built in ADC inputs. It would be simple to just use the LM35 and the xbee/power supply and be done.
     
  8. Col

    Thread Starter Member

    Apr 19, 2012
    44
    2
    For closure.... many of the big IC companies (ADI, maxim etc) have simple temperature sensors requiring no input commands which output a single wire PWM signal, perfect for modulating an RF signal and processing on the receiver side.

    QED :)
     
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