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Circuit for temperature measurement ?

Discussion in 'Electronic Basics' started by Chan, Dec 27, 2003.

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  1. Chan

    Chan Guest

    Hello all,
    In the folowing circuit for temperature measurement

    there is a sensor device. As it is not indicated what this
    device is I was wondering if someone can hazard a guess
    to what it could be, or suggest something that would fit
  2. JeB

    JeB Guest

    definately "hazard"ing ... take a look a LM335.
  3. CFoley1064

    CFoley1064 Guest

    Hello all,
    Hi, Chan. I think you've got an AD590 two-terminal temperature-to-current
    converter, manufactured by Analog Devices. Its output is 1 microamp per degree
    Kelvin, which would give you 273uA at 0 degrees C, and 373uA at 100 degrees C.
    Referring to the schematic, here's the non-technical way of looking at the

    Assuming the - input of the op amp is at gnd potential, the more the temp goes
    up, the more current the AD590 pulls out of the node, the more the op amp
    output has to put in to keep it in balance. So, the op amp output voltage will
    increase linearly as temperature rises.

    The neat thing about the AD590 is that it's pretty much impervious to voltage
    drops from wiring, so the sensor can be some distance from the amplifier. It
    was one of the first real IC temperature sensors. The down side is that it's a
    little pricey. Depending on accuracy desired, Newark sells different classes
    of AD590 from $6.50 to $95.00 USD each. Intersil makes a cross for the JH
    suffix only.

    Good luck
  4. Chan

    Chan Guest

    looks like the other poster is correct as the component should
    be a temperature dependent current source, whereas the
    LM335 is a voltage source. But useful to have in mind all the

    Thanks all.
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