Re: LM35 Temperature Sensor Design Help - LM35 circuit.bmp (1/1) - Article 2355 - go-pugleaf

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Re: LM35 Temperature Sensor Design Help - LM35 circuit.bmp (1/1)

#2355

From: Thomas
Date: Thu, 02 Jan 2003 20:31

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Antony N. Lord wrote:
>>  Actually, the LM35 and variants are more accurate than most commercial
>>thermometers; one has to shell out a fairly good chunk of change to get
>>a calibrated thermometer as good as or better than these ICs.
>>  No calculations, lines of best fit, or any other trash like that.
> 
> 
> I suppose that is true - but surely there has to be calculations / 
> adjustments made due to voltage loss etc. in the cable run between the 
> sensor and the interface.

You could run 4 wires: 2 to feed the sensor, and 2 to read the value back.

> More importantly - any clue as to bringing the maximum output voltage 
> (at the upper measuring temperature point) closer to the 4095mV level.
> 
> It seems pointless not to be using the "full scale" of the input board.

Place an opamp close to the sensor. A pair of resistors will determine your 
scale error. 2% is easy, with 1 resistors 1% each. But 2% of 273K is a LOT.


Thomas

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