Andrew M Errington wrote:

>
> Hi to any analogue gurus,
>
> I want to use a National Semiconductor LM355 absolute temperature sensor to
> measure ambient temperature.  This 3pin device behaves as a zener diode
> whose voltage is linearly proportional to absolute temperature.  At 25degC
> you get 2.982 volts (=298.2Kelvin), and the voltage changes by 10mV per
> degree.
>
> I want everything to operate on a single rail 5V supply, so I need to put
> the output of the sensor into a circuit which has a gain of about 4, and
> which subtracts about 2.6V from the sensor output first.  This will give me
> a sensible output voltage range which can be read using an ADC (connected to
> a PIC of course!)
>

You can use the LM35 part. This will save you the need to substruct 2.6V
to get the reading you want.

Eyal Oppenheimer
E-mail: eyalo@aks.com
R&D
Aladdin Knowledge Systems Ltd.
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