How to calculate resistance values to amplify output of LM35 with opampfor temp 20-90deg C(1deg resolution)?

Question

Sagar E.

Answer 1

The LM35 produces a nicely scaled output already of 10 mV/degree C. At 20 C, this output would be 20 x 10mV = 200 mV. At 90 C, the output would be 90 x 10 mV = 900 mV.

To rescale this using an opamp circuit, the best circuit is a noninverting topology in which the LM35 output would go directly to the op amp + input (noninverting input) and two resistors would set the gain of the op amp circuit to be 1 + R2/R1 where R2 is a resistor from op amp output to op amp - input and R1 is op amp - input to ground. See the wiki link below and scroll down to the noninverting op amp circuit for more description of this circuit.

You have to define further what voltage you want the output scaled to? 20 to 90 degrees C would already be 200 to 900 mV with the LM35 without an op amp and could be digitized directly by an ADC. If you wanted to scale it up some, I would scale based on 100 C which would be 1 V out of the LM35. Lets say you wish to scale this so that 100 C is really 5 V out of the op amp. Then the desired overall gain is:

Gain = Vout/Vin = 5 Volts / 1 Volt (at 100 C) = 5

Gain of noninverting op amp = 1 + R2/R1 = 5
R2 / R1 = 4
Let R1 = 1 KOhm, then R2 = 4 KOhm.

Answer 2

which human beings are no longer heavily thinking? Do you advise the scientists who purchase into the regulations of Nature without question? considering is the way it fairly is taught -- and the regulations are incorrect, a minimum of the regulation of Conservation of Mass and the regulations of diffusion, the definition of mass, and somewhat some theories are corrupt. Or do you advise the religiously susceptible who're no longer serious with regards to the character is supplied in religious texts. i'm puzzled right here. i think of scientists who do no longer heavily think of with regards to the regulations sell atheism. you're somewhat perfect. If the scientists heavily concept with regards to the regulations they might quickly learn that each physique regulations emanate from a single concept - like the Universe originated from a single factor. If scientists found out that each physique regulations originate from a single suited concept, and positively considered it heavily, they'd not be merchandising atheism, somewhat the different, because of the fact religious texts propound that existence (the nicely-known regulations) originated from the trademarks. If scientists have been extra serious, they may be merchandising spirituality, because of the fact their arguments might align with religious texts. There seems to be a underlying false impression approximately people who lived earlier the creation of technology, that someway those human beings have been dense, as though purely enlightened and smart human beings have suddenly regarded after the popularity of the clinical approach. i detect it no longer uncomplicated to have self assurance that Viscount St. Albans, Newton, Einstein... have been smarter than Moses, Elijah, Jesus, .... as though miraculously smart human beings regarded interior the previous couple of centuries.