[time-nuts] Low CostTemperature sensor

Scott Stobbe scott.j.stobbe at gmail.com
Tue Jan 17 09:10:12 EST 2017


 Thermometry based on Diode leakage current wouldn't be impossible I
suppose, you might loose some hair in the process.

The signal levels on the opamp are goofed too.

On Tue, Jan 17, 2017 at 4:19 AM Charles Steinmetz <csteinmetz at yandex.com>
wrote:

> Tom wrote:
>
>
>
> > That article has a major error. Anyone know what it is?
>
>
>
> Well, the author says the reverse current of a diode is "directly"
>
> proportional to temperature.  This could suggest that he means the
>
> relationship is linear (the relationship is actually exponential with
>
> absolute temperature).  But that's not really an *error* -- just sloppy.
>
>   "Direct" does not necessarily imply "linear."  An exponential
>
> relationship is "direct" in the sense that it is what mathematicians
>
> call "injective" (every temperature corresponds to exactly one value of
>
> reverse current).
>
>
>
> Then, in discussing the LM95235, he says that it can use the
>
> "collector-emitter junction diode" of a transistor as the sense element.
>
>   Of course, a bipolar transistor has no collector-emitter junction.
>
> His diagram correctly shows a diode-connected NPN operating in the
>
> active region (forward biased, not reverse biased as the rest of his
>
> article discusses) as the sensor for the LM95235.
>
>
>
> Are any of these what you had in mind, or is there more?
>
>
>
> Charles
>
>
>
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